Question

A chain of length L is placed on a horizontal surface as shown in figure. At any instant X is the length of chain on rough surface and the remaining portion lies on smooth surface. Initially X = 0. A horizontal force P is applied to the chain (as shown in figure). In the duration X changes from X = 0 to X = L for chain to move with constant speed –

• A. The magnitude of P should increase with time
• B. The magnitude of P should decrease with time
• C. The magnitude of P should increase first and then decrease with time
• D. The magnitude of P should decrease first and then increase with time

Answer 1

Answer: (A)

The magnitude of P should increase with time

Answer 2

For chain to move with constant speed P needs to be equal to frictional force on the chain as the length of chain on the rough surface increases. Hence the friction force f_K = µ_K N increases.