Question

In the previous question, the smallest kinetic energy at the bottom of the incline will be achieved by
(a) the solid sphere
(b) the hollow sphere
(c) the disc
(d) all will achieve same kinetic energy.

Answer 1

(b) the hollow sphere

Torque is same for all the bodies; therefore, the angular momentum will be conserved.
Now, total kinetic energy = $\frac{1}{2}m{v}^2+\frac{L^2}{2I}$
So, the body with greater value of moment of inertia will have smallest kinetic energy at the bottom of the incline.

Order of the moment of inertia of the bodies:
hollow sphere > disc > solid sphere

Hence, the hollow sphere will have the smallest kinetic energy at the bottom.