A shell, in flight, explodes into four unequal parts. Which of the following is conserved?

A machine gun of mass $10\,kg$ fires $20\,g$ bullets at the rate of $180$ bullets per minute with a speed of $100\,m s ^{-1}$ each. The recoil velocity of the gun is $.............\,m/s$

Two billiard balls of mass $0.05\,kg$ each moving in opposite directions with $10\,ms ^{-1}$ collide and rebound with the same speed. If the time duration of contact is $t=0.005\,s$, then $\dots N$is the force exerted on the ball due to each other.

A shell of mass $m$ moving with velocity $v$ suddenly breaks into $2$ pieces. The part having mass $m/3$ remains stationary. The velocity of other part will be

A bullet of $'4\,g'$ mass is fired from a gun of mass $4 \,{kg}$. If the bullet moves with the muzzle speed of $50\, {ms}^{-1}$, the impulse imparted to the gun and velocity of recoil of gun are :

A man is standing on a balance and his weight is measured. If he takes a step in the left side, then weight