Question

A toy train P of mass 0.50 kg is travelling along a straight track with a velocity of 3.0m/s. It collides with a stationary train Q of mass 1.0 kg. The two trains then stick together.

What is the velocity of the combined trains?

A 1.0m/s in the same direction as P was travelling originally

B 1.0m/s in the reverse direction to that in which P was travelling originally

C 1.5m/s in the same direction as P was travelling originally

D 1.5m/s in the reverse direction to that in which P was travelling originally

Answer 1

Answer: A.

Explanation:

Toy Train P mass = 0.50kg

V = 3.0 m/s

Toy train Q mass = 1.0kg

Initial Momentum = Mass of P x Velocity of P + Mass of Q x Velocity of Q

                 = 0.50 kg x 3.0 m/s + 1.0 kg x 0 m/s

                 = 1.5 kg m/s

Final Velocity = Total Momentum / Total Mass

              = 1.5 kg m/s / 1.5 kg

              = 1.0 m/s

A 1.0m/s in the same direction as P was traveling originally