2 bodies of different masses of 2 kg and 4 kg are moving with velocities `20 m//s` and 10 m//s towards each other due to mutual gravitational attraction. What is the velocity of their centre of mass?

Options

A. 5m/s
B. 6m/s
C. 8m/s
D. zero

Answer

D

Explanation

`m_(1)=2kg,m_(2)=4kg,vecv_(1)=20m//s,vecv_(2)=-10m//s`
`vecv_(cm)=(m_(1)vecv_(1)+m_(2)vecv_(2))/(m_(1)+m_(2))=(2xx10-4xx10)/(2+4)=0m//s`