If a man jumps out from a boat to the bank of the river,the boat moves backwards. Identify the action and reaction in this situation.

$m_{1}$ and $m_{2}$ masses of two blocks are connected by a light spring on a smooth horizontal surface. The two masses are pulled apart and then released. Prove that the ratio of their acceleration is inversely proportional to their masses.

Two identical bullets are fired,one by a light rifle and another by a heavy rifle with the same force. Which rifle will hurt the shoulder more and why?

Two friends,Girish and Neeraj,were discussing Newton's third law. They were perplexed about how action and reaction are equal and opposite. They could not think of an experiment by which they could ascertain this fact. Pushkar,who was their friend,told them that he would set up an experiment to prove this to them. By performing an experiment,Pushkar demonstrated the law.
$(a)$ Can you think of an experiment by which you can demonstrate this law?
$(b)$ What values do you think Pushkar has?

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.

$A$ girl of mass $50 \, kg$ jumps out of a moving boat of mass $300 \, kg$ onto the bank with a horizontal velocity of $3 \, m s^{-1}$. With what velocity will the boat begin to move backwards (in $, m s^{-1}$)?