Question

In thefollowing example, try to identify the number of times the velocityof the ball changes:

“Afootball player kicks a football to another player of his team whokicks the football towards the goal. The goalkeeper of the oppositeteam collects the football and kicks it towards a player of his ownteam”.

Alsoidentify the agent supplying the force in each case.

Answer 1

Thevelocity of the ball changes four times.

Asa football player kicks the football, its speed changes from zero toa certain value. As a result, the velocity of the ball gets changed.In this case, the player applied a force to change the velocity ofthe ball. Another player kicks the ball towards the goal post. As aresult, the direction of the ball gets changed. Therefore, itsvelocity also changes. In this case, the player applied a force tochange the velocity of the ball. The goalkeeper collects the ball. Inother words, the ball comes to rest. Thus, its speed reduces to zerofrom a certain value. The velocity of the ball has changed. In thiscase, the goalkeeper applied an opposite force to stop/change thevelocity of the ball. The goalkeeper kicks the ball towards his teamplayers. Hence, the speed of the ball increases from zero to acertain value. Hence, its velocity changes once again. In this case,the goalkeeper applied a force to change the velocity of the ball.