Sand is being dropped on a conveyor belt at the rate of $M \ kg/s$. The force necessary to keep the belt moving with a constant velocity of $v \ m/s$ will be

In the first second of its flight,a rocket ejects $1/60$ of its mass with a velocity of $2400\,m/s$. The acceleration of the rocket is ............ $m/s^2$.

$A$ rifle of $20 \,kg$ mass can fire $4$ bullets per second. The mass of each bullet is $35 \times 10^{-3} \,kg$ and its final velocity is $400 \,ms^{-1}$. What force must be applied on the rifle so that it does not move backwards while firing the bullets (in $\,N$)?

$A$ conveyor belt is moving with a constant velocity $V$. Sand is being dropped on the belt at the rate of $M \text{ kg/s}$. The force necessary to keep the belt moving with a constant velocity $V \text{ m/s}$ will be

$A$ Diwali rocket of mass $100\,g$ lifts up with an acceleration of $5\,m/s^2$. If gases eject out of the rocket at a rate of $10\,g/s$,then find the velocity of ejection of gas with respect to the rocket in $m/s$.

$Assertion$ : $A$ rocket moves forward by pushing the surrounding air backwards.
$Reason$ : It derives the necessary thrust to move forward according to Newton's third law of motion.