Two blocks of masses 20 kg and 5 kg are connected by a spring of negligible mass and placed on a frictionless horizontal surface. An impulse gives a velocity of 15 m/s to the heavier block in the direction of lighter block. The velocity of centre of mass is

Options

A. 22 `ms^(-1)`
B. 30 `ms^(-1)`
C. 12 `ms^(-1)`
D. 15 `ms^(-1)`

Answer

c

Explanation

`V_(cm) =(m_(1)v_(1)+m_(2)v_(2))/(m_(1) + m_(2))[v_(1) = 15 m//s, v_(2) = 0, m_(1) = "20 kg m"_(2) = 5 kg]`
`V_(cm) = (20 xx 15 + 5 xx 0)/(25) = (300)/(25) = 12`