$A$ bullet of mass $10\, g$ is fired from a rifle. The bullet takes $0.003\, s$ to move through its barrel and leaves with a velocity of $300\, m s^{-1}$. What is the force exerted on the bullet by the rifle (in $, N$)?

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?

When balanced forces act on a body,the body is

$(a)$ State the law of conservation of momentum.
$(b)$ Mention two factors which determine the momentum of a body.
$(c)$ Prove the law of conservation of momentum with clear explanation,diagram and equation.

State Newton's second law of motion.

$(a)$ State Newton's second law of motion and show that the first law of motion can be mathematically derived from the mathematical expression for the second law of motion.
$(b)$ A stone dropped from a window reaches the ground in $0.5 \, s$ (given $g = 10 \, m \, s^{-2}$):
$(i)$ Calculate the speed just before it hits the ground.
$(ii)$ What is the average speed during $0.5 \, s$?
$(iii)$ Calculate the height of the window from the ground.