Question

In football, a goalkeeper stops a ball. This is due to:
(A) friction between the ball and hand of the goal keeper
(B) the decrease in speed of ball due to air resistance
(C) application of force by goal keeper
(D) all of the above

Answer 1

Hint: By Newton’s law of motion, the moving object will have some force, to stop the moving object the same amount of force or the force maximum to the force of the moving object is given in the opposite direction of the moving object, then only the moving object will stop.

Complete step by step answer:
Let us assume the football match, the player will kick the ball towards the goal post so that he gives some force to the football by his legs. Here the force transfer from his legs to the football, the amount of force is given by the football player is directly proportional to the force of the football. Now, football goes towards the goalkeeper. Now the goalkeeper applies the force on the ball in the opposite direction of the motion of the ball, thus the ball stops. The force applied by the goalkeeper on the ball must be greater than the force of the football which comes towards the goalkeeper.

After the football stops in the hands of the goalkeeper, the goalkeeper pulls his hands backward to decrease the rate of change of momentum of the ball, and then the force exerted by the ball is reduced.

Hence, option (C) is the correct answer.

Note:
By Newton’s third law of motion, when the goalkeeper gives some force to the football, the same amount of force will act on the football in opposite direction. For example, when the ball is thrown into the wall with some force, the ball will return with the same amount of force, but in opposite direction.