Two identical discs are positioned on a vertical axis as shown in figure. The bottom disc is rotating at angular velocity….

Q: Two identical discs are positioned on a vertical axis as shown in figure. The bottom disc is rotating at angular velocity ω₀ and has rotational kinetic energy K₀. The top disc is initially at rest. It then falls and sticks to the bottom disc. The change in the rotational kinetic energy of the system is

(a) K₀/2

(b) -K₀/2

(c) -K₀/4

(d) K₀/4

Ans: (b)