Question

Two players kick two footballs at the same time, but the speed and direction of the balls vary. Choose the statement that explains this case ( ) (a) The grass on the ground is different (b) Gravitational pull varies (c) Force applied by the players varies (d) Sizes of the footballs are different​

Answer 1

Given info : Two players kick two footballs at the same time, but the speed and direction of the balls vary.

To check correct option : (a) The grass on the ground is different.

                                          (b) Gravitational pull varies.

                                          (c) Force applied by the players varies.

                                          (d) Sizes of the footballs are different​.

solution : according to Newton's second law of motion, the rate of change of linear momentum of a body is directly proportional to applied force and takes place in the direction in which force acts.

   means, force ∝ change in momentum/time taken

we know, momentum = mass × velocity

so force ∝ (mass × change in velocity)/time taken

now if two player kick two footballs at the same time, but the speed and direction of the balls vary. it means, velocities of the balls vary and hence momentums of them vary.

but from above explanation, it is clear that momentum is directly proportional to applied force. so the force applied on the balls must vary.

Therefore the correct option (d) force applied by the players varies.