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

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.

Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.

An object of mass $100 \,kg$ is accelerated uniformly from a velocity of $5 \,m \,s^{-1}$ to $8 \,m \,s^{-1}$ in $6 \,s$. Calculate the initial and final momentum of the object. Also, find the magnitude of the force exerted on the object.

$A$ $8000 \,kg$ engine pulls a train of $5$ wagons,each of $2000 \,kg$,along a horizontal track. If the engine exerts a force of $40000 \,N$ and the track offers a friction force of $5000 \,N$,then calculate the net accelerating force (in $N$).

How much momentum will a dumbbell of mass $10\, kg$ transfer to the floor if it falls from a height of $80\, cm$? Take its downward acceleration to be $10\, m \,s^{-2}$.