What is the momentum of an object of mass $m$, moving with a velocity $v$?

$A$ motorcar of mass $1200\, kg$ is moving along a straight line with a uniform velocity of $90\, km/h$. Its velocity is slowed down to $18\, km/h$ in $4\, s$ by an unbalanced external force. Calculate the acceleration and change in momentum. Also,calculate the magnitude of the force required.

$A$ truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of $400 \, m$ in $20 \, s$. Find the force (in $N$) acting on it if its mass is $7 \, \text{tonnes}$ $(1 \, \text{tonne} = 1000 \, kg)$.

When a carpet is beaten with a stick,dust comes out of it. Explain.

An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes,state the conditions that must be placed on the magnitude and direction of the velocity. If no,provide a reason.

$A$ batsman hits a cricket ball which then rolls on a level ground. After covering a short distance,the ball comes to rest. The ball slows to a stop because