NTA Abhyas JEE Main2020PhysicsWork, Power and EnergyPractice
A man is holding a chain of mass m and length l such that the lower end of the chain just touches a table. Now the man places half the length of the chain very slowly on the table while keeping the other half vertical. The work done by the man in this process is
Options
- A– m g l 2
- B– m g l 4
- C– 3 m g l 8
- D–   m g l 8
Correct answer
C. – 3 m g l 8
Step-by-step solution
The work done by man is negative of magnitude of decrease in potential energy of chain. Δ U = m g L 2 – m 2 g L 4 = 3 m g L 8 ∴ W = – 3 m g l 8