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

State the law of conservation of momentum. How does conservation of momentum take place in each of the following?
$(i)$ $A$ rocket taking off from ground.
$(ii)$ Flying of a jet aeroplane.

State whether the following statement is true or false:
$1 \ N$ is the force that produces an acceleration of $1 \ m \ s^{-2}$ in a body of mass $1 \ g$.

$A$ machine gun can fire $50 \, g$ bullets with a velocity of $150 \, m s^{-1}$. $A$ $60 \, kg$ stone is moving towards the machine gun with a velocity of $10 \, m s^{-1}$. How many bullets must be fired from the gun to just stop the stone in its tracks?

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?

$A$ force can be completely described by