Physics-
General
Easy
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 the figure ). In the duration x changes from x = 0 to x = L, for chain to move with constant speed:
- the magnitude of P should increase with time
- the magnitude of P should decrease with time
- the magnitude of P should increase first and then decrease with time
- the magnitude of P should decrease first and then increase with time
The correct answer is: the magnitude of P should increase with time
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 
N increases.
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