A flat car of mass `m` is at rest on a frictionless floor with a child of mass `m` standing at its edge. If the child jumps off from the car towards right with an initial velocity `u`, with respect to the car, find the velocity of the car after its jump.

Explanation

Let the car attain velocity `v`. The velocity of the child with respect to the earth will be `u-v`, as `u` is its velocity with respect to the ear.
Initially, the system was at rest, thus according to momentum conservation, momentum after jump must be zero. Hence,

`m(u-v)Mvimpliesv=("mu")/(m+M)`