Which has a higher value of momentum: $A$ bullet of mass $10 \, g$ moving with a velocity of $400 \, m s^{-1}$ or a cricket ball of mass $400 \, g$ thrown with a speed of $90 \, km h^{-1}$?

$A$ constant force of friction of $50 \ N$ is acting on a body of mass $200 \ kg$ moving initially with a speed of $15 \ m \ s^{-1}$. How long does the body take to stop? What distance will it cover before coming to rest?

What are the changes possible on an object at rest if we apply on it:
$(a)$ a balanced force?
$(b)$ an unbalanced force?

Two friends on roller-skates are standing $5\, m$ apart facing each other. One of them throws a ball of $2\, kg$ towards the other,who catches it. How will this activity affect the position of the two? Explain your answer.

Define momentum and state its $SI$ unit. State the principle of conservation of momentum.

$(a)$ $(i)$ Define momentum. State its $SI$ unit.
$(ii)$ An object of mass $50 \ kg$ is accelerated uniformly from a velocity of $4 \ m/s$ to $8 \ m/s$ in $8 \ s$. Find the magnitude of the force exerted on the object.
$(b)$ State Newton's first law of motion.