A block of mass m slides with velocity v along a frictionless level surface towards a block of mass 4m initially at rest. The velocity of centre of mass is

Options

A. v/5
B. v/4
C. 5v/2
D. (4/5)v

Answer

A

Explanation

Here, `m_(1)=m, v_(1)=v," "m_(2)=4m, v_(2)=0, " "v_(CM)=?`
`v_(CM)=(m_(1)v_(1)+m_(2)v_(2))/(m_(1)+m_(2))=(m times v+4m times 0)/(m+4m)=v/5`