System shown in figure is released from rest . Pulley and spring is mass less and friction is absent everywhere. The speed of `5 kg` block when `2 kg` block leaves the constant of with ground is (force constant of spring `k = 40 N//m and g = 10 m//s^(2))`

Options

A. `sqrt(2) m//s`
B. `2 sqrt(2) m//s`
C. `2 m//s`
D. `sqrt(2) m//s`

Answer

B

Explanation

`x = (2g)/(K)` , from conservation of mechanical energy , `mgx = (1)/(2) Kx^(2) + (1)/(2) mv^(2)`, here `m = 5 kg`.