Kinetic energy increase with an initial velocity

[Dave]

This is really one for aspiring physics teachers.

There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.

Gravitational drop:
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s

Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy

Also works out with speed and distance, s=ut + 1/2at^2

Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125

This is basic secondary school physics

Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.

Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.

150g on 20kg shouldn't affect the calculations too much.

However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.

To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG

Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J

Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J

Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J

Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J

The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.

So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics

With A you've lost a student, and they will go and do something else.

Problems are from
1- my understanding of what is taught
or
2- what is being taught

Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters

Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".

Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

[Dave]

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

If someone plugs in the numbers to special and general relativity, and
it all adds up, I'd be happy. This really means that both need to be
taught from day one to get anything to make good sense. A bit like
learning piano, if you think you can learn tunes with one hand and then
do both later, it's an awful lot harder. Single note keyboard playing
is a dead end, difficult to get out of.

[Jim Pennino]

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?

1. You don't really understand the math and physics.

2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

[Dave]

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me

which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

[Jim Pennino]

Post by Dave

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me
which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

The "flaw" is in YOUR interpretation of the math results.

You fail to understand that total kinetic energy is an exponential
function of total velocity and what that means.

You plug the numbers into a calculator and get a result but have zero
understanding why the results are what they are.

Perhaps a good course in analytic geometry might help.

As for the B answer, since the ENTIRE planet has agreed on the math for
about 300 years, who is this enemy the planet has been trying to keep
stupid for 300 years?

Would that be the lizard people?

[Dave]

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me
which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

The "flaw" is in YOUR interpretation of the math results.
You fail to understand that total kinetic energy is an exponential
function of total velocity and what that means.

Doesn't wash. E= 0.5mv^2, using classical mechanics.

Can't complain as there is no contract. If someone is paying you e.g.
light work in the jail, you should to talk to your supervisor.

[Jim Pennino]

Post by Dave

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me
which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

The "flaw" is in YOUR interpretation of the math results.
You fail to understand that total kinetic energy is an exponential
function of total velocity and what that means.

Doesn't wash. E= 0.5mv^2, using classical mechanics.

Like I said:

The "flaw" is in YOUR interpretation of the math results.

You fail to understand that total kinetic energy is an exponential
function of total velocity and what exponential means even though
you can quote the correct formula.

A good course in analytic geometry may be able to fix that if you pay
attention in class.

[Dave]

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me
which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

The "flaw" is in YOUR interpretation of the math results.
You fail to understand that total kinetic energy is an exponential
function of total velocity and what that means.

Doesn't wash. E= 0.5mv^2, using classical mechanics.

The "flaw" is in YOUR interpretation of the math results.
You fail to understand that total kinetic energy is an exponential
function of total velocity and what exponential means even though
you can quote the correct formula.
A good course in analytic geometry may be able to fix that if you pay
attention in class.

You're not making a considered point. You're also not giving a correct
interpretation. So there is no conclusion agreed, yet. Using "weight of
authority" and not "reasoned argument" is poor. Anyone who can't answer
the point shouldn't be in teaching.

Regarding class: 3D modelling is something I should get around to.
However physics is a lot more complicated with stretchy /bendy space-
time, likely won't ever get to this, but others can. Interesting with
improvements for rotational inertia, and so on.

[Jim Pennino]

Post by Dave

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me
which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

The "flaw" is in YOUR interpretation of the math results.
You fail to understand that total kinetic energy is an exponential
function of total velocity and what that means.

Doesn't wash. E= 0.5mv^2, using classical mechanics.

The "flaw" is in YOUR interpretation of the math results.
You fail to understand that total kinetic energy is an exponential
function of total velocity and what exponential means even though
you can quote the correct formula.
A good course in analytic geometry may be able to fix that if you pay
attention in class.

You're not making a considered point. You're also not giving a correct
interpretation. So there is no conclusion agreed, yet. Using "weight of
authority" and not "reasoned argument" is poor. Anyone who can't answer
the point shouldn't be in teaching.
Regarding class: 3D modelling is something I should get around to.
However physics is a lot more complicated with stretchy /bendy space-
time, likely won't ever get to this, but others can. Interesting with
improvements for rotational inertia, and so on.

Irrelevant babble.

Go to https://www.desmos.com/calculator.

As E= 0.5mv^2 is of the form E = v^2, type that into the equation bar.

Use the + and - buttons to zoom in and out.

Notice how a very small change in v makes a huge difference in E.

[Dave]

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me
which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

As for the B answer, since the ENTIRE planet has agreed on the math for
about 300 years, who is this enemy the planet has been trying to keep
stupid for 300 years?

British Naval gunnery ruled the waves for about 100 years. Losing to
the Americans with their freedom struggle was a great shock, so a lot of
effort was put in, and the Establishment wouldn't have given away the
solution for free. They had the right charts to land a shell on a deck,
or palace, from 20 miles away. There was a previous discussion about the
inaccuracy of Carnot Cycle efficiency, since the goal was high pressure
steam.

Post by Jim Pennino
Would that be the lizard people?

They (the gods) are getting bored, and want to see regular people in
flying saucers. Unfortunately unless everyone understands the right
physics nothing will get no-where. In WW2 the Germans tried a bit, but
Project Paperclip was only a partial success after the war.

[Jim Pennino]

Post by Dave

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me
which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

As for the B answer, since the ENTIRE planet has agreed on the math for
about 300 years, who is this enemy the planet has been trying to keep
stupid for 300 years?

British Naval gunnery ruled the waves for about 100 years. Losing to
the Americans with their freedom struggle was a great shock, so a lot of
effort was put in, and the Establishment wouldn't have given away the
solution for free. They had the right charts to land a shell on a deck,
or palace, from 20 miles away. There was a previous discussion about the
inaccuracy of Carnot Cycle efficiency, since the goal was high pressure
steam.

Irrelevant and silly babble.

The entire world uses the same physics.

Everybody in the world used range tables for artillery until computer
aiming came along. Since they are gun, powder charge and projectile
specific they were mostly generated empirically until computers came along.

Naval gunnery has nothing to do with high pressure steam.

Post by Dave

Post by Jim Pennino
Would that be the lizard people?

They (the gods) are getting bored, and want to see regular people in
flying saucers. Unfortunately unless everyone understands the right
physics nothing will get no-where. In WW2 the Germans tried a bit, but
Project Paperclip was only a partial success after the war.

Insane babble.

Actually, Project Paperclip was an almost total success and it seems
you have no clue what Project Paperclip actually was.

[Dave]

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me
which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

The "flaw" is in YOUR interpretation of the math results.
You fail to understand that total kinetic energy is an exponential
function of total velocity and what that means.
You plug the numbers into a calculator and get a result but have zero
understanding why the results are what they are.
Perhaps a good course in analytic geometry might help.
As for the B answer, since the ENTIRE planet has agreed on the math for
about 300 years, who is this enemy the planet has been trying to keep
stupid for 300 years?

How about this one? Under freedoms granted by Article 9 of the European
Convention on Human Rights, 666 as given in the New Testament Book of
Revelation, is about the male:female ratio. i.e. there are 666 men out
of 1000 people, so a male:female ratio of 2:1, which is why they need so
many wars.

Explains the trans movement and equality movements to an extent. The
50:50 ratio is a lie which they have tried to keep going for at least
1700 years.

Don't judge societies who don't have an equal male:female ratio in
business, or try to force equality in the numbers.

[Jim Pennino]

Post by Dave

Post by Jim Pennino

Post by Dave

Post by Jim Pennino

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s) Speed(m/s) Kinetic Energy Height Needed (m)
1 10 1000 J 5
2 20 4000 J 20
3 30 9000 J 45
4 40 16000 J 80
5 50 25000 J 125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0J 1000J 1000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 1000J 4000J 3000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 25000J 36000J 11000J
Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 10,000,000J 10,201,000J 201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers. What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Which is more likely here?
1. You don't really understand the math and physics.
2. Every physicist on the planet since the time of Newton has been
involved in a continuing, giant conspiracy for some unknown reason.

Unfortunately you've given an A answer: shut up and stop annoying me
which shows you don't understand it either. I'm after a B answer - the
correct physics, i.e. the flaw in the calculations or thought experiment
pointed out.

The "flaw" is in YOUR interpretation of the math results.
You fail to understand that total kinetic energy is an exponential
function of total velocity and what that means.
You plug the numbers into a calculator and get a result but have zero
understanding why the results are what they are.
Perhaps a good course in analytic geometry might help.
As for the B answer, since the ENTIRE planet has agreed on the math for
about 300 years, who is this enemy the planet has been trying to keep
stupid for 300 years?

How about this one? Under freedoms granted by Article 9 of the European
Convention on Human Rights, 666 as given in the New Testament Book of
Revelation, is about the male:female ratio. i.e. there are 666 men out
of 1000 people, so a male:female ratio of 2:1, which is why they need so
many wars.
Explains the trans movement and equality movements to an extent. The
50:50 ratio is a lie which they have tried to keep going for at least
1700 years.
Don't judge societies who don't have an equal male:female ratio in
business, or try to force equality in the numbers.

Just another pile of blithering nonsense.

[Dave]

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Current conclusion after some chat:
Classical physics doesn't describe the real universe very well, but an
idealised one. It isn't even self consistent at the human scale (new
insight thanks to rocket sled thought experiment).

I am willing to change on new information given.

Specifically problems exist with kinetic energy and momentum. Kinetic
energy comes from the conservation of energy (conversion of
gravitational potential energy to kinetic energy) and acceleration in
free fall at the same rate.

Am I bothered - no I'm retired. Others might be. Also in no good
conscience could I teach the classical mechanics, since I'm not coming
across eternal truths. If I were hard up, yes, I would regurgitate for pay.

[Jim Pennino]

Post by Dave

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation of
energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size for
a little rocket engine. Uses about 150g of fuel (mostly oxidiser) per
second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount - not
near light speed.
To get to the initial speed is beside the point, could use a big rubber
band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you say to
a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Classical physics doesn't describe the real universe very well, but an
idealised one. It isn't even self consistent at the human scale (new
insight thanks to rocket sled thought experiment).
I am willing to change on new information given.

Take a course in analytical geometry and the new information you will be
given will include:

Equations of the form y = ax^2 describe a parabola.

The first derivative of an equation describes the slope of the curve
for all points x and for this equation the derivative is 2ax.

From this it becomes immediately obvious that for values of x > 1/2a
the slope becomes much bigger than 1.

That means any incremental change in x results in an ever growing
increase in y.

QED

This is sophomore high school math, or at least it was when I went to
high school.

<snip nonsense>

[Dave]

Post by Dave

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation
of energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size
for a little rocket engine. Uses about 150g of fuel (mostly oxidiser)
per second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount -
not near light speed.
To get to the initial speed is beside the point, could use a big
rubber band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic energy,
makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you say
to a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Classical physics doesn't describe the real universe very well, but an
idealised one. It isn't even self consistent at the human scale (new
insight thanks to rocket sled thought experiment).
I am willing to change on new information given.
Specifically problems exist with kinetic energy and momentum. Kinetic
energy comes from the conservation of energy (conversion of
gravitational potential energy to kinetic energy) and acceleration in
free fall at the same rate.
Am I bothered - no I'm retired.  Others might be. Also in no good
conscience could I teach the classical mechanics, since I'm not coming
across eternal truths. If I were hard up, yes, I would regurgitate for pay.

Makes more sense with the change in speed proportional to the distance
dropped, not the time falling. Why would the acceleration depend on the
initial speed?

This would keep a consistency with the conservation of energy in a good
way, the rocket sled, and momentum and kinetic energy are harmonised.

Can't think of everything all at once, and thanks to Jim, the thread has
been kept alive for this information to arrive (after good sleep). Might
also explain why the only British lander on Mars crashed badly.

Hope to give updated numbers very soon.

[Dave]

Post by Dave

Post by Dave

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg), conservation
of energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size
for a little rocket engine. Uses about 150g of fuel (mostly oxidiser)
per second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount -
not near light speed.
To get to the initial speed is beside the point, could use a big
rubber band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic
energy, makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you say
to a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Classical physics doesn't describe the real universe very well, but an
idealised one. It isn't even self consistent at the human scale (new
insight thanks to rocket sled thought experiment).
I am willing to change on new information given.
Specifically problems exist with kinetic energy and momentum. Kinetic
energy comes from the conservation of energy (conversion of
gravitational potential energy to kinetic energy) and acceleration in
free fall at the same rate.
Am I bothered - no I'm retired.  Others might be. Also in no good
conscience could I teach the classical mechanics, since I'm not coming
across eternal truths. If I were hard up, yes, I would regurgitate for pay.

Makes more sense with the change in speed proportional to the distance
dropped, not the time falling. Why would the acceleration depend on the
initial speed?
This would keep a consistency with the conservation of energy in a good
way, the rocket sled, and momentum and kinetic energy are harmonised.
Can't think of everything all at once, and thanks to Jim, the thread has
been kept alive for this information to arrive (after good sleep). Might
also explain why the only British lander on Mars crashed badly.
Hope to give updated numbers very soon.

i.e. Have acceleration due to gravity in a drop as velocity increase per
meter dropped.

It might be that everything is still consistent with accepted basics,
don't know at this stage. Acceleration as velocity increase per unit
time is so engrained it might take a while to move on from this.

Energy to move stuff up is E=mgh. This is self evident, irrespective of
units. Moving heavy stuff up takes more effort, and moving it up further
takes more effort. Seems linear for both variables close to the planet.

[Dave]

Post by Dave

Post by Dave

Post by Dave

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg),
conservation of energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size
for a little rocket engine. Uses about 150g of fuel (mostly
oxidiser) per second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount -
not near light speed.
To get to the initial speed is beside the point, could use a big
rubber band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic
energy, makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you
say to a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Classical physics doesn't describe the real universe very well, but
an idealised one. It isn't even self consistent at the human scale
(new insight thanks to rocket sled thought experiment).
I am willing to change on new information given.
Specifically problems exist with kinetic energy and momentum. Kinetic
energy comes from the conservation of energy (conversion of
gravitational potential energy to kinetic energy) and acceleration in
free fall at the same rate.
Am I bothered - no I'm retired.  Others might be. Also in no good
conscience could I teach the classical mechanics, since I'm not
coming across eternal truths. If I were hard up, yes, I would
regurgitate for pay.

Makes more sense with the change in speed proportional to the distance
dropped, not the time falling. Why would the acceleration depend on
the initial speed?
This would keep a consistency with the conservation of energy in a
good way, the rocket sled, and momentum and kinetic energy are
harmonised.
Can't think of everything all at once, and thanks to Jim, the thread
has been kept alive for this information to arrive (after good sleep).
Might also explain why the only British lander on Mars crashed badly.
Hope to give updated numbers very soon.

i.e. Have acceleration due to gravity in a drop as velocity increase per
meter dropped.
It might be that everything is still consistent with accepted basics,
don't know at this stage. Acceleration as velocity increase per unit
time is so engrained it might take a while to move on from this.
Energy to move stuff up is E=mgh.  This is self evident, irrespective of
units. Moving heavy stuff up takes more effort, and moving it up further
takes more effort.  Seems linear for both variables close to the planet.

Redefining kinetic energy as E=mV (not bothered about units at this
stage)- you could always multiply by an arbitrary constant.

Mass = 20kg.

Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
0 10 0 200 200

Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
10 20 200 400 200

Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
50 60 1000 1200 200

Initial Speed after Initial KE Final KE KE increase
speed (m/s) burn(m/s)
1000 1010 20000 20200 200

Same energy input gives the same energy increase in kinetic energy.
E=0.5mv^2 is not consistent with the conservation of energy on the
rocket sled. Conservation of energy (no free energy) has been proven in
the courts of the land.

[Jim Pennino]

Post by Dave

Post by Dave

Post by Dave

Post by Dave

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg),
conservation of energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size
for a little rocket engine. Uses about 150g of fuel (mostly
oxidiser) per second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount -
not near light speed.
To get to the initial speed is beside the point, could use a big
rubber band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic
energy, makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you
say to a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Classical physics doesn't describe the real universe very well, but
an idealised one. It isn't even self consistent at the human scale
(new insight thanks to rocket sled thought experiment).
I am willing to change on new information given.
Specifically problems exist with kinetic energy and momentum. Kinetic
energy comes from the conservation of energy (conversion of
gravitational potential energy to kinetic energy) and acceleration in
free fall at the same rate.
Am I bothered - no I'm retired.  Others might be. Also in no good
conscience could I teach the classical mechanics, since I'm not
coming across eternal truths. If I were hard up, yes, I would
regurgitate for pay.

Makes more sense with the change in speed proportional to the distance
dropped, not the time falling. Why would the acceleration depend on
the initial speed?
This would keep a consistency with the conservation of energy in a
good way, the rocket sled, and momentum and kinetic energy are
harmonised.
Can't think of everything all at once, and thanks to Jim, the thread
has been kept alive for this information to arrive (after good sleep).
Might also explain why the only British lander on Mars crashed badly.
Hope to give updated numbers very soon.

i.e. Have acceleration due to gravity in a drop as velocity increase per
meter dropped.
It might be that everything is still consistent with accepted basics,
don't know at this stage. Acceleration as velocity increase per unit
time is so engrained it might take a while to move on from this.
Energy to move stuff up is E=mgh.  This is self evident, irrespective of
units. Moving heavy stuff up takes more effort, and moving it up further
takes more effort.  Seems linear for both variables close to the planet.

Redefining kinetic energy as E=mV (not bothered about units at this
stage)- you could always multiply by an arbitrary constant.

And everything after that would be wrong.

That E = (mV^2)/2 has been known to be true for hundreds of years and is a
trivial experiment to perform.

<babbling nonsense snipped>

[Dave]

Post by Dave

Post by Dave

Post by Dave

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg),
conservation of energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size
for a little rocket engine. Uses about 150g of fuel (mostly
oxidiser) per second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount -
not near light speed.
To get to the initial speed is beside the point, could use a big
rubber band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic
energy, makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you
say to a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Classical physics doesn't describe the real universe very well, but
an idealised one. It isn't even self consistent at the human scale
(new insight thanks to rocket sled thought experiment).
I am willing to change on new information given.
Specifically problems exist with kinetic energy and momentum. Kinetic
energy comes from the conservation of energy (conversion of
gravitational potential energy to kinetic energy) and acceleration in
free fall at the same rate.
Am I bothered - no I'm retired.  Others might be. Also in no good
conscience could I teach the classical mechanics, since I'm not
coming across eternal truths. If I were hard up, yes, I would
regurgitate for pay.

Makes more sense with the change in speed proportional to the distance
dropped, not the time falling. Why would the acceleration depend on
the initial speed?
This would keep a consistency with the conservation of energy in a
good way, the rocket sled, and momentum and kinetic energy are
harmonised.
Can't think of everything all at once, and thanks to Jim, the thread
has been kept alive for this information to arrive (after good sleep).
Might also explain why the only British lander on Mars crashed badly.
Hope to give updated numbers very soon.

i.e. Have acceleration due to gravity in a drop as velocity increase per
meter dropped.
It might be that everything is still consistent with accepted basics,
don't know at this stage. Acceleration as velocity increase per unit
time is so engrained it might take a while to move on from this.
Energy to move stuff up is E=mgh.  This is self evident, irrespective of
units. Moving heavy stuff up takes more effort, and moving it up further
takes more effort.  Seems linear for both variables close to the planet.

BTW summoned my muse Cassandra accidently watching lots of Led Zeppelin
and Ned's Atomic Dustbin videos online. She also says that when
dropping something you are likely to lose half the energy since you put
all the work in, but on a drop, half the energy goes into moving the
planet up to you. Probably where the 0.5 comes from. She wants everyone
to be nice to each other, AND get things correct.

[Jim Pennino]

Post by Dave

Post by Dave

Post by Dave

Post by Dave

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg),
conservation of energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size
for a little rocket engine. Uses about 150g of fuel (mostly
oxidiser) per second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount -
not near light speed.
To get to the initial speed is beside the point, could use a big
rubber band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic
energy, makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you
say to a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Classical physics doesn't describe the real universe very well, but
an idealised one. It isn't even self consistent at the human scale
(new insight thanks to rocket sled thought experiment).
I am willing to change on new information given.
Specifically problems exist with kinetic energy and momentum. Kinetic
energy comes from the conservation of energy (conversion of
gravitational potential energy to kinetic energy) and acceleration in
free fall at the same rate.
Am I bothered - no I'm retired.  Others might be. Also in no good
conscience could I teach the classical mechanics, since I'm not
coming across eternal truths. If I were hard up, yes, I would
regurgitate for pay.

Makes more sense with the change in speed proportional to the distance
dropped, not the time falling. Why would the acceleration depend on
the initial speed?
This would keep a consistency with the conservation of energy in a
good way, the rocket sled, and momentum and kinetic energy are
harmonised.
Can't think of everything all at once, and thanks to Jim, the thread
has been kept alive for this information to arrive (after good sleep).
Might also explain why the only British lander on Mars crashed badly.
Hope to give updated numbers very soon.

i.e. Have acceleration due to gravity in a drop as velocity increase per
meter dropped.
It might be that everything is still consistent with accepted basics,
don't know at this stage. Acceleration as velocity increase per unit
time is so engrained it might take a while to move on from this.
Energy to move stuff up is E=mgh.  This is self evident, irrespective of
units. Moving heavy stuff up takes more effort, and moving it up further
takes more effort.  Seems linear for both variables close to the planet.

BTW summoned my muse Cassandra accidently watching lots of Led Zeppelin
and Ned's Atomic Dustbin videos online. She also says that when
dropping something you are likely to lose half the energy since you put
all the work in, but on a drop, half the energy goes into moving the
planet up to you. Probably where the 0.5 comes from. She wants everyone
to be nice to each other, AND get things correct.

Childish babble.

[Dave]

Post by Dave

Post by Dave

Post by Dave

Post by Dave
This is really one for aspiring physics teachers.
There are issues with kinetic energy between a rocket,
and a gravitational drop both in a vacuum.
gravity is 10ms-2. i.e. every second the velocity increases by 10m/s
Say mass = 20 kg
Kinetic energy is taught as E=1/2m v^2.
Height needed to get to the energy with E=mgh, h=E/(mg),
conservation of energy
Also works out with speed and distance, s=ut + 1/2at^2
Time(s)   Speed(m/s)  Kinetic Energy     Height Needed (m)
1           10          1000 J            5
2           20          4000 J            20
3           30          9000 J            45
4           40         16000 J            80
5           50         25000 J            125
This is basic secondary school physics
Now with a rocket in a vacuum in space, or on a frictionless sled.
No wheels so no complexity from rotational inertia.
Using F=ma, Newtons law, a 20kg mass, and a thrust of 200N, to get
an acceleration of 10m/s. It so happens that 200N is a standard size
for a little rocket engine. Uses about 150g of fuel (mostly
oxidiser) per second.
150g on 20kg shouldn't affect the calculations too much.
However there are interesting things when the rocket is given an initial
velocity. A one second burn uses the same energy (mass of fuel), and
should increase the speed so the kinetic energy by the same amount -
not near light speed.
To get to the initial speed is beside the point, could use a big
rubber band.
KE- kinetic energy, 1/2 m v^2.
M - 20KG
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
0              10           0J         1000J      1000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
10             20           1000J      4000J      3000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
50             60           25000J     36000J     11000J
Initial      Speed after   Initial KE Final KE  KE increase
speed (m/s)    burn(m/s)
1000           1010      10,000,000J 10,201,000J  201,000J
The same burn gives a completely different increase in kinetic
energy, makes no sense presented like this.
So this is really one for aspiring physics teachers.  What do you
say to a smart kid who challenges you with this?
A- shut up and stop annoying me
B- give the correct physics
With A you've lost a student, and they will go and do something else.
Problems are from
1- my understanding of what is taught
or
2- what is being taught
Regarding 1- this is well below light speed, so relativistic refinements
shouldn't apply, and the drop is all quite near the earth, so gravity
can be seen as constant, over say several hundred meters
Regarding 2- there are good reasons why the would want to teach
an incorrect information, to keep the enemy stupid. Unfortunately
what was good in about year 1903, is now holding us back. The "lie" has
become the accepted "truth".
Would love a "correct" physics, since what is being taught is likely
what is keeping people back from making more advanced aerial craft.

Classical physics doesn't describe the real universe very well, but
an idealised one. It isn't even self consistent at the human scale
(new insight thanks to rocket sled thought experiment).
I am willing to change on new information given.
Specifically problems exist with kinetic energy and momentum. Kinetic
energy comes from the conservation of energy (conversion of
gravitational potential energy to kinetic energy) and acceleration in
free fall at the same rate.
Am I bothered - no I'm retired.  Others might be. Also in no good
conscience could I teach the classical mechanics, since I'm not
coming across eternal truths. If I were hard up, yes, I would
regurgitate for pay.

Makes more sense with the change in speed proportional to the distance
dropped, not the time falling. Why would the acceleration depend on
the initial speed?
This would keep a consistency with the conservation of energy in a
good way, the rocket sled, and momentum and kinetic energy are
harmonised.
Can't think of everything all at once, and thanks to Jim, the thread
has been kept alive for this information to arrive (after good sleep).
Might also explain why the only British lander on Mars crashed badly.
Hope to give updated numbers very soon.

i.e. Have acceleration due to gravity in a drop as velocity increase per
meter dropped.
It might be that everything is still consistent with accepted basics,
don't know at this stage. Acceleration as velocity increase per unit
time is so engrained it might take a while to move on from this.
Energy to move stuff up is E=mgh.  This is self evident, irrespective of
units. Moving heavy stuff up takes more effort, and moving it up further
takes more effort.  Seems linear for both variables close to the planet.

For the drop, assume that freefall acceleration starts and measures at
9.8ms^2, very successfully and in vacuum chambers in various countries
for 100s of years.

s=ut + 1/2 at^2
v=u+at
So in 1 second s= 0.5x10 * 1*1 = 5m fall in a second
So speed increases to 10m/s in 1 second

Speed increase rate is 2m/s per meter.

The speed increases with distance, not time. (Cassandra Physics)
For conservation of energy with E=mgh,

Air resistance is ignored 20kg mass.
Input energy is mgh, but not the regular g, but G (from Cassandra) at 2

Height Speed Input energy(mGh) Kinetic Energy (m*v)
G is 2
5 10 200 (20*2*5) 200
10 20 400 (20*2*10) 400
20 40 800 800
30 60 1200 1200
40 80 1600 1600
50 100 2000 2000
60 120 2400 2400
70 140 2800 2800
100 200 4000 (20*2*100) 4000
150 300 6000 (20*2*150) 6000
200 400 8000 (20*2*200) 8000
1000 2000 40000 (20*2*1000) 40000

So there you have it, all self consistent.

If I'm wrong I'll post a grovelling apology
(concept, not the sums, regular apology for bad arithmetic).

If they have been teaching the wrong physics, there is a need a great
purging of professors
Either:
1- they have been teaching wrong facts knowing what is correct,
thus confusing people and bringing education into disrepute - why
believe them on climate change, guilt by association is only human
or
2- they should have worked out the basics and should be fired
for stupidity (ignorant repeater).

[Jim Pennino]

In sci.physics Dave <***@yahoo.com> wrote:

<snip piles of old crap>

Post by Dave
For the drop, assume that freefall acceleration starts and measures at
9.8ms^2, very successfully and in vacuum chambers in various countries
for 100s of years.
s=ut + 1/2 at^2
v=u+at
So in 1 second s= 0.5x10 * 1*1 = 5m fall in a second
So speed increases to 10m/s in 1 second
Speed increase rate is 2m/s per meter.

The rate of speed increase is acceleration and has units of ms^-2.

Post by Dave
The speed increases with distance, not time. (Cassandra Physics)

S(t) = S0 + V0*t + (a * t^2)/2 = S0 + .5*(V0 + V(t))*t

V(t) = V0 + a*t

V^2(t) = V0^2 + 2*a*[S(t) -S0]

Where

t is elapsed time
S0 is the initial displacement from the origin
S(t) is the displacement from the origin at time t
V0 is the inital velocity
V(t) is the velocity at time t
a is the acceleration

If x is the position, v is the velocity, a the acceleration and t is
time:

v = dx/dt

a = dv/dt and also the second derivative of x.


<snip nonsense>