$A$ book of mass $2 \, kg$ is sliding with a constant velocity of $4 \, m s^{-1}$ on a frictionless horizontal table. What is the force required to keep the object moving with the same velocity (in $, N$)?

$(a)$ When a motorcar makes a sharp turn at a high speed,we tend to get thrown to one side. Why?
$(b)$ State Newton's first and third law of motion.
$(c)$ $A$ force of $5 \ N$ gives a body of mass $m$ an acceleration of $10 \ m \ s^{-2}$. Calculate the mass of the body in grams.

Write the relation for the collision of two balls $A$ and $B$ and state the related law.

$(a)$ Define momentum. Write its $SI$ unit.
$(b)$ $A$ car and a truck have the same momentum. Whose velocity is more and why?
$(c)$ $A$ bullet of mass $20 \ g$ moving with a speed of $500 \ m s^{-1}$ strikes a wooden block of mass $1 \ kg$ and gets embedded in it. Find the speed with which the block moves along with the bullet.

Show that the rate of change of momentum $=$ mass $\times$ acceleration.

$A$ goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to