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9 Oct 2008 18:55:51 IST
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Conceptual ques - Rotational Mechanics
On a frictionless floor, a person is rotating on skates. He pulls his arms in. So moment of inertia desreases, and so, according to conservation of angular momentum, the angular velocity increases, and net rotational Kinetic energy decreases.
Question : Where does this extra energy come from?
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10 Oct 2008 19:03:21 IST
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and net rotational Kinetic energy decreases.
Actually net kinetic energy will not decrease but will increase as KE=L2/2I
here L is constant while I is decreasing hence KE shouid increase....
Question : Where does this extra energy come from?
while pulling his arms some work will be done by man and energy will come from his internal energy.
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10 Oct 2008 19:14:19 IST
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wen d person contracts his arms some work is done by him...dat's it....rate if useful
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10 Oct 2008 19:49:28 IST
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Sorry.... that was mistyping...
actually the KE increases (i mistyped it as "decreases")
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10 Oct 2008 19:51:10 IST
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The man pulls his arms in.
but that's inside the system.
no work was done by any external force. then why does the KE increase?
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11 Oct 2008 21:24:32 IST
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Hmm edit
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11 Oct 2008 21:40:37 IST
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So simple........ When the man pulls his hands inside, the rotational inertia decreases and the angular velocity increses.............. So while one increses, the other decreses...... conserved
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11 Oct 2008 21:41:16 IST
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One more thing, are you sure its frictionless
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