Question

A football player kicks a football to another player of his team who kicks it towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team.

The momentum of football changes:

• A. two times
• B. three times
• C. one time
• D. four times

Answer 1

The correct option is D

four times

As we know, the Momentum of the body is the product of mass and velocity. Momentum is a vector quantity because it has magnitude as well as direction.

$p=mv$

Here, p = momentum of the body

m = mass of the object

v = velocity of the object

Observing the situation where momentum gets changed:

1. When a football player kicks a football at another player (ball from rest, starts moving): 1st time
2. Another player kicks it toward the goal (ball changes the direction): 2nd time
3. The goalkeeper of the opposite team collects the football (ball comes to rest from motion): 3rd time
4. And the goalkeeper kicks it towards the player of his own team (ball from rest, starts moving again): 4th time.

Therefore, a total of four times change in momentum of the ball is taking place.

Hence option (d) is correct.