When a force of $40\, N$ is applied on a body,it moves with an acceleration of $5\, m s^{-2}$. Calculate the mass of the body. (in $kg$)

During a game of table tennis,if the ball hits a player,it does not hurt him. On the other hand,when a fast-moving cricket ball hits a spectator,it may hurt him. State the reason.

Two cars each of mass $1000 \ kg$ are moving in a straight line but in opposite directions. The velocity of each car is $5 \ m s^{-1}$ before the collision during which they stick together. What will be the velocity of the combined cars after collision (in $m s^{-1}$)?

Which has the highest inertia among solids made of aluminium,steel,and wood of the same shape and same volume?

What would happen if a fielder stops a fast-moving ball suddenly? Justify your answer.

$(i)$ Define momentum. Write its $SI$ unit.
$(ii)$ How much momentum will an object of mass $10 \ kg$ transfer to the floor if it falls from a height of $5 \ m$? $(g = 10 \ m \ s^{-2})$
$(iii)$ Explain how a karate player can break a pile of tiles with a single blow of his hand.