Two block of mass `2kg` are connected by a massless ideal spring of spring contant `K=10N//m` . The upper block is suspended from roof by a light string `A` . The system shown is in equilibrium. The string `A` is now cut, the acceleration of upper block just after the string `A` is cut will be `(g=10m//s^(2)` .

Answer

20

Explanation

Before the string A is cut let x be elongation in the spring
As system is in equilibrium, then for lower block, kx = mg = 20 N

Just after the string A is cut
For upper block, kx + mg = ma

2a = 20 + 20 , `a = 20 m//s^(2)`