Question

A point mass of 1 kg collides elastically with a stationary point mass of 5 kg. After their collision, the 1 kg mass reverses its direction with a speed of 2 m/s. Which of the following statements is correct?

(a) Both masses move with the same speed.
(b) Both masses move in opposite directions.
(c) The 1 kg mass comes to rest.
(d) The 5 kg mass moves with a speed of 0.4 m/s.

Answer 1

Both masses move in opposite directions.

Step-by-step explanation:

When a point mass of 1 kg collides elastically with a stationary point mass of 5 kg, and after their collision, if the 1 kg mass reverses its direction with a speed of 2 m/s, it means that both masses move in opposite directions.

In an elastic collision, both momentum and kinetic energy are conserved. Since the 1 kg mass reverses its direction, it means that the momentum is conserved, and the 5 kg mass will also move but in the opposite direction. However, the 5 kg mass will have a different speed since it has more mass. Therefore, the correct statement is (b) Both masses move in opposite directions.