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

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

$A$ 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.

An object of mass $1 \,kg$ travelling in a straight line with a velocity of $10\, m\, s^{-1}$ collides with,and sticks to,a stationary wooden block of mass $5\, kg$. Then they both move off together in the same straight line. Calculate the total momentum just before the impact and just after the impact. Also,calculate the velocity of the combined object.

Akhtar, Kiran, and Rahul were riding in a motorcar that was moving with a high velocity on an expressway when an insect hit the windshield and got stuck on the windscreen. Kiran suggested that the insect suffered a greater change in momentum compared to the motorcar. Akhtar said that since the motorcar was moving with a larger velocity, it exerted a larger force on the insect. Rahul said that both the motorcar and the insect experienced the same force and the same change in momentum. Comment on these suggestions.

Why is it advised to tie any luggage kept on the roof of a bus with a rope?