Question

A small block is placed on a horizontal platform which undergoes horizontal S.H.M about a mean position ‘O’.The block does not slip on the platform. Force of friction acting on the block is f.

• A. ‘f’ is always directed towards ‘O’
• B. f is directed towards ‘O’ when the block is moving away from ‘O’ and f is directed away from ‘O’ when the block is moving towards ‘O’
• C. f = 0 when block and platform come to momentary rest at the extreme position of S.H.M
• D. f is maximum when block and platform come to momentary rest at the extreme position of S.H.M

Answer 1

Answer: (A), (D)

The correct options are
A ‘f’ is always directed towards ‘O’
D f is maximum when block and platform come to momentary rest at the extreme position of S.H.M

The only horizontal force acting on the block is frictional force (f) Hence ‘f’ is the force responsible for block to perform SHM and is always directed forwards ‘O’. At the extreme position, the value of f(static friction) becomes maximum.