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

Options

A. `sqrt(2)m//s`
B. `2sqrt(2)m//s`
C. `2m//s`
D. `4sqrt(2)m//s`

Answer

B

Explanation

The system ………………..
`F.B.D` of `2 kg` block

When `2kg` block just leaves the contact
`N = 0`
`kx+0=20 implies x = (20)/(40) = (1)/(2)m`
Applying `WET` for the whole system
`w_(g)+w_(s f)= Delta k`
`implies 50xx(1)/(2)-(1)/(2)(40)[((1)/(2))^(2)-0]= (1)/(2)(5)[V^(2)-0]`
`implies V = 2sqrt(2) m//s`