Violation of conservation of angular momentum

[Doc Al]

It's difficult to follow your example. Please restate it without any wildly unphysical "infinities". Where do you see energy being created? (Note that in a real tetherball case there is gravity pulling the ball down.)

 

[Haelfix]

Conservation of angular momentum is a mathematical theorem, its simply unavoidable. Its proved in any number of ways in most elementary books on mechanics. Try as you like to find a counter example, and they can get arbitrarily complicated, you won't succeed without making a mistake (and sometimes the mistake can be made arbitrarily subtle).

 

[pallidin]

I have read this thread with great interest, as well as the link to another thread given at the beginning. I have a question:

If the tether ball is released from the string just before it's spiral motion impacts the pole, would it travel farther than is accounted for from the initial impact force of hitting the ball it the first place?
Hope my question makes any sense.

 

[pallidin]

If I am understanding all of this correctly, there is a net gain in energy, but that the energy source is the torque resistance of planet Earth within that frame of reference.

 

[eosphorus]

"If the tether ball is released from the string just before it's spiral motion impacts the pole, would it travel farther than is accounted for from the initial impact force of hitting the ball it the first place?""

the trick of the tetherball is that the linear speed remains constant however the radius so when it hits or is relesed from the pole the energy is the same either kinetic when released or transformed in heat and noise when hitting


take a tehterball 1kg mass 1 m initial radius 1 million kilometers final radius

take an Earth 1000 tons mass so gravity gets really weak

create amomentum on the tetherball of 1 and the Earth has o momentum of 0

lets suppose a thickness of the pole of 1 m and the thickness of the cable of 0

the tetherball starts to unwind, its been agreed that the tetherball keeps a constant linear velocity however the radius and that a torque is exerced on the pole and transferred to Earth because of its thickness

the linear speed of the ball is the same and there's a constant torque on the earth

the ball gains angular momentum from the Earth because the radius increases from 1 m to 1 million km and the linear speed remains at 1 m/s

the Earth gains torque from 0 to a big number because the radius of the thickness of the pole and the tension of the string have created this torque

both the torque of the Earth and the angular momentum of the Earth will add a total momentum of one the initial one

 

[ZapperZ]

You still have not shown ANY understanding of the fact that the tetherball in your example undergoes coupling with an external source.

If you still think you have found a violation of angular momentum, you are welcome to submit to the IR section. This thread has gone nowhere but round and round and round like the tetherball. It is now done.

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