Question

Masses of given blocks are $m_A=m_B=3$ kg
$m_C=$ 4 kg and $m_D=$ 2 kg. System is initially at rest.
As soon as string connecting C and D is burnt, . [Take g = m/$s^2$]

• A. Acceleration of block C is 5 m/$s^2$ upward.
• B. Acceleration of block D is 10 m/$s^2$ downward.
• C. Acceleration of block C is 2 m/$s^2$ upward.
  
• D. Acceleration of block A is 2 m/$s^2$ downward.

Answer 1

Answer: (A), (B)

The correct options are
A Acceleration of block C is 5 m/$s^2$ upward.
B Acceleration of block D is 10 m/$s^2$ downward.

Tension in string with spring can not change until spring expands or compresses. So tensions in springs between C & A and between A and B do not change as soon as the string is burnt. So acceleration of A & B is zero & for C $\Rightarrow$

a = $\frac{60-40}{4}=5m/s^2$