A heavy body moving with a velocity $30\, m/s$ and another small object at rest undergo  an elastic collision. The latter will move with a velocity of .............. $\mathrm{m}/ \mathrm{s}$

Two balls $A$ and $B$ having masses $1\, kg$ and $2\, kg$, moving with speeds $21\, m/s$ and $4\, m/s$ respectively in opposite direction, collide head on. After collision Amoves with a speed of $1\,m/s$ in the same direction, then correct statements is :

A rod $AB$ is free to rotate in a vertical plane about a horizontal axis through $A$ as shown in figure. It is slightly disturbed from rest in its position of unstable equilibrium and when it is next vertical the end $B$ collides with a fixed peg and rebounds. If the rod comes to instantaneous rest when $AB$ is horizontal (as shown in figure) then :-

A body of mass $1\,kg$ collides head on elastically with a stationary body of mass $3\,kg$. After collision, the smaller body reverses its direction of motion and moves with a speed of $2\,m / s$. The initial speed of the smaller body before collision is $..........ms ^{-1}$

A body of mass $4\  kg$ collides head-on elastically with another body of mass $2\  kg$ kept at rest in free space. Time of collision is $0.02\  sec$ and average impulse force acted on each bodies is $100\  N$. Find the velocity of the $2\  kg$ body after the impact

Which of the following statements is true