$A$ cricket ball of mass $70 \, g$,moving with a velocity of $0.5 \, m s^{-1}$ is stopped by a player in $0.5 \, s$. What is the force applied by the player to stop the ball (in $, N$)?

During a game of table tennis,if the ball hits a player,it does not hurt him. On the other hand,when a fast-moving cricket ball hits a spectator,it may hurt him. State the reason.

The velocity-time graph of a ball of mass $20 \ g$ moving along a straight line on a level ground is given below. How much force does the ground exert on the ball to bring it to rest?

What is the force required to accelerate a $2 \, kg$ mass by $5 \, m s^{-2}$ (in $, N$)?

$A$ certain force exerted for $1.2 \, s$ raises the speed of an object from $1.8 \, m s^{-1}$ to $4.2 \, m s^{-1}$. Later, the same force is applied for $2 \, s$. How much does the speed change in $2 \, s$?

Chetan's father wanted to buy a car. He visited many showrooms to find out the price and the specifications of various cars. In one of the showrooms,he was told by the salesman that their car had excellent brakes such that the car stops instantaneously. Chetan's father was impressed and decided to buy that car. In the evening,he discussed this with his family. Chetan told his father that such a car cannot be made and the salesman had lied to him. He told his father that he should not buy that car and,moreover,never from that showroom. He explained to his father why it is not possible. His father was convinced and promised to visit another showroom and be careful this time.
$(a)$ What might have been the explanation given by Chetan to convince his father?
$(b)$ What values do you see in Chetan?