$A$ gun recoils after firing to conserve

When a missile is fired from a tank,it gets a momentum of $2000 \ kg \ m \ s^{-1}$. If the velocity of the missile is $50 \ m \ s^{-1}$,what will be its mass (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.

$A$ constant force acts on an object of $5 \ kg$ for a period of $2 \ s$. It increases the velocity of the object from $3 \ m s^{-1}$ to $7 \ m s^{-1}$. Find the magnitude of the applied force. Now,if the force were applied for a period of $5 \ s$,what would be the final velocity of the object?

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?

Which of the following statements is not correct for an object moving along a straight path in an accelerated motion?