The quantity that is not conserved in an inelastic collision is

A ball strikes a horizontal surface as shown in figure. If co-efficient of restitution $e = 1/ \sqrt 3$,  then angle $\theta$ is  ............... $^o$

Aball of mass $m$ collides elastically with an identical ball at rest with some impact parameter.

A particle of mass $m$ moving with a speed $v$ hits elastically another stationary particle of mass $2\ m$ in a fixed smooth horizontal circular tube of radius $R$. Find the time when the next collision will take place?

A molecule in a gas container hits a hortzontal wall with speed $200 \;m s ^{-1}$ and angle $30^{\circ}$ with the normal, and rebounds with the same speed. Is momentum conserved in the collision? Is the collision elastic or inelastic?

A ball of mass $m$ is moving with a speed $V$ as shown in the figure. It undergoes inelastic collision with a ball of mass $2\ m$ which was initially at rest. The velocity of ball $2\ m$ after collision will be given by