re: energy producing experiments

[Delburt Phend]

Oops; I was thinking of the ball being thrown; but Q said dropped. That means that the ball accelerates toward the earth and the earth accelerates toward the ball. They have equal and opposite momentum.

The earth's momentum can not be measured but we have to assume that it bounces back away from the point of collision just like the 2 gram ball. The ball keeps its momentum and the earth keeps its momentum. There is no momentum transfer.  The only noticeable motion will be that of the ball.

[Low-Q]

Oops; I was thinking of the ball being thrown; but Q said dropped. That means that the ball accelerates toward the earth and the earth accelerates toward the ball. They have equal and opposite momentum.

The earth's momentum can not be measured but we have to assume that it bounces back away from the point of collision just like the 2 gram ball. The ball keeps its momentum and the earth keeps its momentum. There is no momentum transfer.  The only noticeable motion will be that of the ball.

It does not matter if the ball or the earth is in motion. The end result is a total momentum that is conserved. Would it make any difference if you throw the ball into earth, or even throw the ball into a vertical wall that is fixed to the earth, or use a large crane to move a 10000 kg concrete block towards a stationary 2 grams steel ball? Would the steel ball fly away as a projectile? Nope!
If I understood you correctly, you assume that the earth must have motion and hit a stationary small ball, and not the other way around. If so, your assumption is not correct. The energy and momentum is conserved in any case.


and it does not matter if you throw or drop the ball. The ball gains momentum as it accelerate towards the earth, and the earth gains the very same momentum as it accelerate towards the ball. The earths acceleration is however very tiny, but it's there.


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[telecom]

It does not matter if the ball or the earth is in motion. The end result is a total momentum that is conserved. Would it make any difference if you throw the ball into earth, or even throw the ball into a vertical wall that is fixed to the earth, or use a large crane to move a 10000 kg concrete block towards a stationary 2 grams steel ball? Would the steel ball fly away as a projectile? Nope!
If I understood you correctly, you assume that the earth must have motion and hit a stationary small ball, and not the other way around. If so, your assumption is not correct. The energy and momentum is conserved in any case.


and it does not matter if you throw or drop the ball. The ball gains momentum as it accelerate towards the earth, and the earth gains the very same momentum as it accelerate towards the ball. The earths acceleration is however very tiny, but it's there.


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The earth doesn't haver any momentum because its linear speed equals 0.
The momentum of the ball is conserved, this is why it reflects back with the same momentum it had before the impact less losses.

[Delburt Phend]

Place two masses in deep space, the only gravitational attraction is from each other.

One of the masses is ten kilograms and the other is one kilogram.

From Newton's Third Law we know that the mutual attraction is equal in both directions.

From F = ma we know that the acceleration of the one kilogram will be ten times greater than the acceleration of the 10 kilograms.

After a period of time the one kilogram will be moving 10 times faster than the 10 kilograms. When the one kilogram is moving one meter per second the 10 kilograms will be moving .1m/sec.

Then ½ *10kg *.1 m/sec * .1 m/sec = .05 joules

And ½ * 1 kg * 1 m/sec* 1 m/sec = .5 joules

Energy is not conserved. 

If the 2 gram ball had another source for it's velocity the acceleration of the two spheres would not be interdependent and therefor they would not have equal momentum.

[Low-Q]

Place two masses in deep space, the only gravitational attraction is from each other.

One of the masses is ten kilograms and the other is one kilogram.

From Newton's Third Law we know that the mutual attraction is equal in both directions.

From F = ma we know that the acceleration of the one kilogram will be ten times greater than the acceleration of the 10 kilograms.

After a period of time the one kilogram will be moving 10 times faster than the 10 kilograms. When the one kilogram is moving one meter per second the 10 kilograms will be moving .1m/sec.

Then ½ *10kg *.1 m/sec * .1 m/sec = .05 joules

And ½ * 1 kg * 1 m/sec* 1 m/sec = .5 joules

Energy is not conserved. 

If the 2 gram ball had another source for it's velocity the acceleration of the two spheres would not be interdependent and therefor they would not have equal momentum.

Energy conservation does not mean that the two balls must have the same energy. "Conservation" of some quantity in Physics means that the value of the quantity at some time t1 is the same as the value as another time, t2. If you calculate the total energy of the system when it starts moving and at a later time, they will have the same energy. You need to consider potential energy of the system and the sum of the kinetic energies to get the total mechanical energy.

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