Question

How much work is done on a body of mass 1 kg whirling on a circular path of radius 5 m?

Explain with complete calculations & justifications.

Answer 1

we know any body do work when a Force act on body and by applying this force body take some distance .
now we see here body have mass and weight downward but body have no linear motion, body rotating only own axis . so, here no work will be done by body . but body have torque , angular momentum etc due to body rotate so, his reason body has moment of inertia .

Answer 2

A force is required for a body moving in a circular path and we know that it is centripetal force Fc which is directed towards the centre of the circle.
At the same time, if we see the figure, displacement of a body at a point is given by the tangent .
we know that radius is perpendicular to the tangent at a point.
work done = force x displacement x cos Teta.
= FxSxcos 90 ( since angle between force and displacement is 90)
=0 ( since cos 90 = 0)
therefore, we can say that work done on body whirling in circular path is zero.