A small, light pulley is attached with a block C of mass 4 kg as shown in fig. Block B of mass 1.5 kg is placed on the top horizontal surface of C. Another block A of mass 2 kg is hanging from a string, attached with B and passing over the pulley. Taking `g=10ms^(-2)` and neglecting friction, calculate the acceleration of each block when the system is released from rest.

Options

A. All the statement are correct.
B. Only I, II and IV are correct.
C. Only I,and II are correct.
D. Only II and IV are correct.

Answer

B

Explanation

Before cutting the string, the tension in string joining `m_(4)` and ground is `T=(m_(1)+m_(2)-m_(3)-m_(4))g`
And the spring force in the spring joing `m_(3)` and `m_(4)` is `T-m_(4)g`.
As the string is cut, the spring force do not change instantly, so just after cutting the string the equilibrium of `m_(1),m_(2)` and `m_(3)` would be maintained but `m_(4)` accelerates in upward direction with acceleration given by
`a=(T+m_(4)g-m_(4)g)/(m_4)`.