Explain the following:
$(i)$ Why does a boatman push the river bank backward with a long bamboo pole when launching his boat into the water?
$(ii)$ Why does a boat tend to leave the shore when passengers are alighting from it? How does the boatman overcome this difficulty?
$(iii)$ Why does a gun recoil when fired?
$(iv)$ How do rockets operate in space?

(N/A) $(i)$ While launching his boat into the water,the boatman pushes the river bank backward with a long pole. In accordance with Newton's third law of motion,the bank applies an equal and opposite reaction force on the pole,thereby pushing the boat forward.
$(ii)$ When passengers alight from the boat,they push the boat in the backward direction. As a result,the boat tends to move away from the shore. The boatman overcomes this by tying the boat to a rigid support on the bank.
$(iii)$ When a bullet is fired,the gun exerts a forward force on the bullet. According to Newton's third law,the bullet exerts an equal and opposite force on the gun,causing it to recoil.
$(iv)$ Rockets operate in space by ejecting burnt gases at high velocity from the rear. According to Newton's third law,the gases exert an equal and opposite reaction force on the rocket,propelling it forward.