Question

Select the correct answer.
Two balls have the same mass. One ball moving along the positive x–axis and the other ball moving along the positive y–axis undergo perfectly inelastic collision. What can you say about the motion of the balls after the collision?

A.
The balls stick and move together.
B.
The balls separate immediately.
C.
The first ball stops while the other ball starts moving.
D.
The two balls travel off in opposite directions, 180° apart.

Answer 1

In a perfectly inelastic collision, the two colliding bodies stick together after the collision.

Given that one ball is moving along the positive x-axis and the other along the positive y-axis, after the collision, they will stick together and move as a single object. The direction of their combined motion can be determined by conserving momentum.

1. Before the collision, the momentum of the first ball (moving along the x-axis) is \( m v_x \) and for the second ball (moving along the y-axis) is \( m v_y \).

2. The total momentum after the collision will be the vector sum of these momenta.

3. The two balls will not split apart or separate since in a perfectly inelastic collision, they stick together.

Thus, the correct answer is:

**A. The balls stick and move together.**