question_answer

Explain, why (a) The passengers are thrown forward from their seats, when a speeding bus stops suddenly. (b) Does a cricketer move his hand backwards while holding a catch? (c) Is the boat pushed away when a man jumps out of the boat?                    

Answer:

                (a) This is due to inertia of motion. When the speeding bus stops suddenly, lower part of the body in contact with the seat stops. The upper part of the body of the passengers tends to maintain its uniform motion. Hence the passengers are thrown forward. (b) When the ball is caught, the impulse received by the hands is equal to the product of the force exerted by the ball and the time taken to complete the catch. By moving the hands backwards, the cricketer increases the time of catch. The force exerted on his hands becomes much smaller and it does not hurt him. (c) Initially, the total momentum of the boat and the man is zero. As the man jumps out of the boat, he gains momentum in the forward direction. To conserve momentum, the boat also gains an equal and opposite momentum. So the boat moves away from the shore.