$A$ man of mass $m$ is standing on a platform of mass $M$ kept on a smooth ice surface. If the man starts moving on the platform with a speed $v$ relative to the platform,with what velocity does the platform recoil relative to the ice?

$A$ bomb at rest explodes into three parts of equal mass. If the momentum of two parts are $-2 p \hat{i}$ and $p \hat{j}$,find the magnitude of momentum of the third part.

$A$ $300 \ kg$ trolley carrying a $25 \ kg$ sandbag is moving on a frictionless track with a uniform speed of $27 \ km/hr$. After some time,sand starts leaking out of the bag at a rate of $0.05 \ kg/s$ and falls onto the floor of the trolley. Find the speed of the trolley in $km/hr$ when the sandbag is completely empty.

$A$ particle of mass $m$ travelling along the $x$-axis with speed $v_0$ shoots out $1/3$ of its mass with a speed $2v_0$ along the $y$-axis. The velocity of the remaining piece is:

$A$ stationary body explodes into two parts of masses $M_{1}$ and $M_{2}$. They move in opposite directions with velocities $v_{1}$ and $v_{2}$. The ratio of their kinetic energies is

State the law of conservation of momentum.