A body of mass $2\,kg$ makes an elastic collision with another body at rest and continues to move in the original direction with one fourth of its original speed. The mass of the second body which collides with the first body is .......... $kg$

A projectile of mass $3m$ is moving at $40\, m/s$ at is highest point, where it breaks into two parts $m$ and $2m$. Mass $2m$ moves vertically up at $25\, m/s$. The other part will move at speed  .................... $\mathrm{m}/ \mathrm{s}$

Two identical balls $A$ and $B$ having velocities of $0.5\, m s^{-1}$ and $-0.3 \, m s^{-1}$ respectively collide elastically in one dimension. The velocities of $B$ and $A$ after the collision respectively will be

A ball falls from a height of $5\,m$ and strikes the roof of a lift. If at the time of collision, lift is moving in the upward direction with a velocity of $1\,m/s$, then the velocity with which the ball rebounds after collision will be $-(e = 1)$

An alpha-particle of mass $m$ suffers $1-$ dimensional elastic collision with a nucleus at rest of unknown mass. It is scattered directly backwards losing, $64\%$ of its initial kinetic energy. The mass of the nucleus is .......... $\mathrm{m}$

A body of mass $2\, kg$ moving with a velocity of $6\, m/s$ strikes inelastically another body of same mass at rest. The amount of heat evolved during collision is ............... $\mathrm{J}$