Question

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))`

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

Answer 1

Correct Answer - B
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`