A block B is placed over a cart which in turn lies over a smooth horizontal floor. Block A and Block C are connected to block B with light inextensible strings passing over light frictionless pulleys fixed to the cart as shown. Initially the blocks and the cart are at rest. All the three blocks have mass m and the cart has mass `M(M=3m)`. Now a constant horizontal force of magnitude F is applied to block A towards right.
Assuming friction to be absent everywhere, the magnitude of acceleration of cart at the shoen instant is

Options

A. `(F)/(6m)`
B. (F)/(4m)`
C. `(F)/(3m)`
D. 0

Answer

D

Explanation

The free body diagram of cart is
Hence net horizontal force on cart is zero.
acceleration of cart is zero.