**Question:**

Two friends on roller-skates are standing 5 metres apart facing each other. One of them throws a ball of 2 $\mathrm{kg}$ towards the other, who catches it. How will this activity affect the position of the two ? Explain.

**Solution:**

When one boy throws a ball towards the other boy, he moves in the backward direction to conserve the linear momentum. On the other hand, the second boy will move away from the first boy after receiving momentum from the ball. Therefore, the distance between two friends will increase.