Doubt 1 : [SOLVED]

A circular disc of radius R has MI equal to I about a perpendicular axis. The radius of the concentric circular part which should be removed so that remaining part has half the MI of disc about the same axis is ?

I tried it by taking MOI of whole disc then subtracting the MOI with distance as x but no answer is matching. Any Hints ?

## Options for Doubt 1

A)

B) R/2

C)

D)

Doubt 2 : [ALMOST SOLVED]

Kinetic energy of a particle moving along a circle of radius r is given by B x^{2} where x is the distance travelled. The resultant acceleration acting on the particle is?

What should be the approach ?