I am helping my son prep for an exam. We have been given the answer of w=.197 rad/s, but we cannot figure out how that is correct.

We have considered rotational kinetic energy of the platform and of the boy along with conservation of momentum, but no luck.

Any assistance would be greatly appreciated. I am not a physics expert and can only help him so much. ]]>

Quote:

An epicyclical gear train has a fixed annular wheel C concentric with sun wheel A. A planet wheel B gears with A and C and can rotate freely on a pin carried by an arm D which rotates about an axis coaxial with that of A and C. If TA and TC are the numbers of teeth on A and C respectively, prove that the ratio of the speeds(rpm) of D to A is equal to the ratio of TA to ( TA + TC) |

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Regards; wanderer. ]]>

I encountered this problem:

A particle of charge Q and mass m is accelerated from rest through a potential difference V, attaining a kinetic energy K. What is the kinetic energy of a particle of charge 2Q and mass m/2 that is accelerated from rest through the same potential difference?

The correct answer is 2K; however, since KE = 1/2mv^2, and U=qV, shouldn't the kinetic energy be K?

Thanks! ]]>