Question

figure shows a system of four pulleys with 2 masses m=3kg and M=4kg at an instant force acting on the block A if block B is going up at an acceleration of 3m/s^2 and pulley Q is going down at an acceleration of 1m/s^2 is

Answer 1

 At an instant force acting on block A if block B is going up at an acceleration of 3m/s2 and pulley Q is going down at an acceleration of 1m/s2 is. Positive sign indicates that block is acceleration at 3.5m/s2 in downward direaction. So, force acting F=3×3.5=10.5N (downward)