The system shown is hanging in equilibrium above the ground. When the string is cut at t=0. The time at which the spring is at its natural length will be (Take `pi^(2)`=10)

Options

A. `g//2` upwards , g downwards
B. g upwards, `g//2` down wards
C. g upwards, `2g` downwards
D. `2g` upwards, g downwards

Answer

A

Explanation

After string is cut, FBD of m
`a=(mg)/(m)=g darr`

FBD of 2m (when string is cut tension in the spring takes finite time to becomes zero. How ever tension in the string immediately become zero.)

`a=(3mg-2mg)/(2m)=g/2 uarr`