Question

Explain the following briefly:
(a) A cricket ball causes much severe injury than a tennis ball on hitting a spectator.
(b) An applied unbalanced force causes a change in momentum.
(c) A greater force is required to impart greater velocity to an object.

Answer 1

A) The very simple reason is that the force acting on the cricket ball is much more than the force acting on a tennis ball. Moreover the mass of the cricket ball is very heavy as compared to tennis . So, when greater force is applied then the ball striking the spectator will also injured him more severely.

B) An applied force can change the momentum as well as the speed of the object as per the physics definition of mementum . If the force is applied it will cause whether to decrease or increase the movement of the object which s actually the change in momentum.

C) When a greater force is applied it cause the change in acceleration ( Newton law) and we know change in acceleration means the change in velocity so when the more force applied  in the direction of motion the velocity is also increased. 

Answer 2

1.(a) A cricket ball causes much severe injury than a tennis ball on hitting a spectator:

A cricket ball ball has more mass than the tennis ball , so the momentum possessed by the Cricket ball will be more than tennis ball. As the momentum is more, change in momentum will be also more, so  when the cricket ball  hits the spectator, the final momentum becomes zero and hence the impact force of the cricket ball is more on hitting a spectator than tennis ball.

b)An applied unbalanced force causes a change in momentum:

When two or more  forces which are unequal in magnitude are acting in the opposite direction of an object, which causes change in the state of motion are called as Unbalanced forces

Unbalanced forces causes acceleration.If Unbalanced forces are acting on an object , then the  velocity of an object increases and hence its momentum also . Because momentum is defined as product of mass and velocity.

c)A greater force is required to impart greater velocity to an object.

According to Newton's Second Law, F=ma
we know that F α a
If force applied on an object  increases ,then acceleration also increases .As acceleration is defined as rate of change of velocity.So acceleration increases, velocity also increases