Figure shows two blocks of masses `5 kg` and `2 kg` placed on a frictionless surface and connected with a spring. An external kick gives a velocity of `14 m//s` to the heavier block in the direction of lighter one. Deduce (a) velocity gained by the centre of mass and (b) the separate velocities of the two blocks in the centre of mass coordinates just after the kick.

Explanation

a. Velocity of centre of mass is
`v_(CM)(5xx14xx2xx0)/(5+2)=10m//s`
b. . Due to the kick on the `5 kg` block, it starts moving with a velocity `14 m//s` immediately, but due to inertia, `2 kg` block remains at rest, at that moment. Thus, velocity of `5 kg` block w.r.t. to centre of mass is `v_(1)=14-10=4m//s`, and velocity of `2kg` block w.r.t to centre of mass is `v_(2)=0-10=-10m//s.`