question_answer

  In the following example, try to identify the number of times the velocity of ball changes: "A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team". Also identify the agent supplying the force in each case.                                                      [NCERT]

Answer:

                  The velocity of ball changes three times. (a)The velocity changes for the first time, when the ball is kicked by football player of one team. So he is the agent who supplies the force in this case. (b) The velocity changes for the second time, when the ball is kicked by another player of same team who naturally becomes the agent supplying force in this case. (c) The velocity changes for the third time, when the ball is kicked by goalkeeper of the opposite team towards a player of his own team. Thus, the agent supplying the force in this case is the goalkeeper.