$A$ 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 $, N$)?

In the following table,the mass and speed of two bodies are given. Which body has more momentum? Justify your answer.

Body	Mass $(kg)$	Speed $(m s^{-1})$
$A$	$1$	$10$
$B$	$2$	$9$

$(a)$ State Newton's second law of motion. Express it mathematically and find the $SI$ unit of force from it.
$(b)$ In the diagram given below, if the card is flicked away with a jerk, what will you observe? Explain the reason for this observation.

What would be the force required to stop a car of mass $1000 \ kg$ and a loaded truck of mass $10000 \ kg$ in $2 \ s$,if they are moving with the same velocity of $5 \ m s^{-1}$?

Newton's first law of motion is also called the law of inertia. Why?

$A$ man weighing $60 \ kg$ runs along the rails with a velocity of $18 \ km \ h^{-1}$ and jumps into a car of mass $1$ quintal $(100 \ kg)$ standing on the rails. Calculate the velocity with which the car will start travelling along the rails. (in $m \ s^{-1}$)