In an elastic collision of two particles,which of the following quantities is conserved?

Two equal masses $m_1$ and $m_2$ moving along the same straight line with velocities $+3 \, m/s$ and $-5 \, m/s$ respectively collide elastically. Their velocities after the collision will be respectively

Which of the following is not a perfectly inelastic collision?

Which of the following statements is true?

$A$ 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 .............. $m/s$.

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