$A$ bomb initially at rest explodes by itself into three equal mass fragments. The velocities of two fragments are $(1\hat{i}+3\hat{j}) \ m/s$ and $(2\hat{i}-4\hat{j}) \ m/s$. The velocity of the third fragment (in $m/s$) is

State and explain the law of conservation of momentum for a system of particles.

$A$ $6 \,kg$ bomb at rest explodes into three equal pieces $P, Q$ and $R$. If $P$ flies with speed $30 \,m/s$ and $Q$ with speed $40 \,m/s$ making an angle $90^{\circ}$ with the direction of $P$. The angle between the direction of motion of $P$ and $R$ is about (in $^{\circ}$)

An explosion breaks a rock into three parts in a horizontal plane. Two of them go off at right angles to each other. The first part of mass $1 \, kg$ moves with a speed of $12 \, m s^{-1}$ and the second part of mass $2 \, kg$ moves with $8 \, m s^{-1}$ speed. If the third part flies off with $4 \, m s^{-1}$ speed,then its mass is ......... $kg$.

At high altitude, a body at rest explodes into two equal fragments. One fragment receives a horizontal velocity of $10 \,ms^{-1}$. The time taken by the two position vectors connecting the point of explosion to the fragments to make an angle of $90^{\circ}$ is (in $\,s$)

$A$ projectile moving vertically upwards with a velocity of $200\, ms^{-1}$ breaks into two equal parts at a height of $490\, m$. One part starts moving vertically upwards with a velocity of $400\, ms^{-1}$. How much time will it take,after the break up,for the other part to hit the ground? .............. $s$