Question

A railroad car of mass M is at rest on frictionless rails when a man of mass m starts moving on the car towards the engine. If the car recoils with a speed v backward on the rails, with what velocity is the man approaching the engine?

Answer 1

Thanks for asking the question!

ANSWER::

Let the mass moving with a velocity x with respect to the engine.

Velocity of the mass with respect to earth is (x-v) towards right.

Centre of mass of V = 0 (initially at rest)

Therefore , 0 = -Mv + m(x-v)

Mv = m(x-v)

mx = Mv + mv

x = [v(M+m)/m]

x = [1 + M/m] v

Hope it helps!