While playing football,the goalkeeper did not get sufficient time to stop a fast ball shot towards him. Why did he hurt his hand while doing so?

$(a)$ Why do we jerk wet clothes before spreading them on a clothesline?
$(b)$ Fruits fall off the branches when a strong wind blows. Give a reason.

$A$ man pushes a box of mass $50\, kg$ with a force of $80\, N$. What will be the acceleration of the box due to this force? What would be the acceleration if the mass were doubled?

Look at the diagram below and answer the following questions:
$(i)$ When a force is applied through the free end of the spring balance $A$,the reading on the spring balance $A$ is $20 \ g \ wt$. What will be the reading shown by the spring balance $B$?
$(ii)$ Write the reason for your answer.
$(b)$ If a balloon is filled with air and its mouth is untied,air is released from its mouth in the downward direction. Write the other observations made by you and justify your answer.

State Newton's second law of motion.

$A$ large truck and a mini bus both moving with a velocity of magnitude $V$ have a head-on collision and both of them come to a halt after that. If the collision lasts for $1 \, s$:
$(a)$ Which vehicle experiences the greater force of impact?
$(b)$ Which vehicle experiences the greater change in momentum?
$(c)$ Which vehicle experiences the greater acceleration?