Mass `m` shown in figure is in equilibrium. If it is displaced further by `x` and released find its acceleration just after it is released. Take pulleys to the light `&` smooth and strings light.

Options

A. `(4kx)/(5m)`
B. `(2kx)/(5m)`
C. `(4kx)/(m)`
D. none of these

Answer

C

Explanation

Initially the block is at rest under action of force `2T` upward and mg downwards. When the block is pulled downwards by `x`. The spring extends by `2x`. Hence tension `T` increases by `2kx`. Thus the net
`therefore` acceleration of the block is `=(4kx)/(m)`