A trolley of negilible mass on horizontal tracks is at rest. A person of mass 50kg is standing on the trolley with a bag of mass 10kg. The person throws the bag off the trolley horizontally with a velocity of 3m/s. Calculate the velocity of the man.

Establish what information you have been given in the question (mass of person=50kg, mass of bag=10kg, velocity of bag=3m/s, start velocity of both=0m/s). Use the equation momentum=mv and the principle of conservation of momentum. This means that the initial momentum of the man and bag is 0 as they are stationary. Therefore mass of bag * 3 = mass of man * v. Solve for v to get 0.6m/s.