Question

Is the kinetic energy of the descending mass really negligible campared with that of the rotating objects as claimed above mgh = (8h^2I)/(D^2t^2) + W_F ?
The ratio of the two kinetic enrgies is 1/2 (m v^2)/(1/2 I w^2). This may easily shown to be:

(1/2 m v^2)/(1/2 I w^2) = (m D^2)/(4 I )

by using v = (w D)/2 .

Answer 1

this seems like an experiment based question .........isn't it ???

I can tell you the concept here. If you have any doubt, let me know

what you need to do is just put the value of mass (m) , diameter (D) and moment of inertia of ring in following equation

(m D^2) / (4 I ) - just solve this equation by putting in the values.

you will most probably get a value with a magnitude of more than 1 which means that the kinetic energy of the descending mass is really negligible compared with that of the rotating objects.