A body of mass '' dropped from a height '' reaches the ground with a sped of . The value of work done by the air-friction is:
- (A)-0.68 mgh✓ Correct
- (B)0.64 mgh
- (C)mgh
- (D)1.64 mgh
Answer: (A)
Solution
By the work–energy theorem, . Starting from rest, the final kinetic energy is , while gravity does . Thus .
JEE Main · 2021 · 01 Sep 2021 · Shift 2 · Single correct option