Question

A pendulum bob is given a push when it is suspended freely.

If bob successfully completes the vertical circle, then least ratio of kinetic energies at bottom and top of the circle is

(a) 2 : 1

(b) 5 : 1

(c) 7 : 1

(d) 1 : 2

Answer 1

Answer is : (b) 5 : 1

For successful rotation,

These values are minimum possible values.

So, ratio of kinetic energies,