$A$ $8000 \,kg$ 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 $N$).

$A$ 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 $7 \, \text{tonnes}$ $(1 \, \text{tonne} = 1000 \, kg)$.

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.

$A$ bullet of mass $10\, g$ travelling horizontally with a velocity of $150\, m/s$ strikes a stationary wooden block and comes to rest in $0.03\, s$. Calculate the distance of penetration of the bullet into the block. Also,calculate the magnitude of the force exerted by the wooden block on the bullet.

$A$ 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