If a man jumps out from a boat to the bank of the river,the boat moves backwards. Identify the action and reaction in this situation.

The qualitative definition of force is given by

State the law of conservation of momentum. Mention two factors which determine the momentum of a body. $A$ ball of mass $0.4 \ kg$ is thrown vertically upwards with a velocity of $10 \ m s^{-1}$. What will be its initial momentum and what would be its momentum at the highest point of its reach? If this change in momentum occurs in one second, find the negatively accelerating force acting on the ball, when it was going up.

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

$A$ bullet of mass $10 \, g$ is fired with a velocity of $400 \, m s^{-1}$ from a gun of mass $4 \, kg$. What is the recoil velocity of the gun (in $, m s^{-1}$)?

$(a)$ How much momentum will an object of mass $10 \ kg$ transfer to the floor if it falls from a height of $0.8 \ m$? $(g = 10 \ m s^{-2})$
$(b)$ Explain why it is difficult for a fireman to hold a hose,which ejects a large amount of water at a high velocity.