$A$ truck starts from rest and rolls down a hill with constant acceleration. It travels a distance of $400 \, m$ in $20 \, s$. Find its acceleration. Find the force acting on it, if its mass is $7$ metric tons.

What is the effect of force when it is applied in the following cases?
$(a)$ $A$ balloon is pressed from opposite sides.
$(b)$ $A$ ball is hit with a bat.
$(c)$ $A$ spring is compressed.

In which direction do the following forces act when an object is in motion?
$(i)$ Frictional force
$(ii)$ Gravitational force
$(iii)$ Centripetal force

Given below are some measuring units of different physical quantities:
$kg\, ms^{-2}, ms^{-2}, kg\, ms^{-1}, ms^{-1}, kg\, m^2 s^{-2}$
Select the units which measure force and momentum respectively.

For a $2 \ kg$ mass,the $v-t$ graph is given. Find the force experienced by the mass in $OA$,$AB$,and $BC$.

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.