A billiard ball moving with a speed of $5 \,m/s$ collides with an identical ball originally at rest. If the first ball stops after collision, then the second ball will move forward with a speed of ...........  $m{s^{ - 1}}$

 A lorry and a car moving with the same $K.E.$  are brought to rest by applying the same retarding force, then

Ball $A$ moving at $12\  m/s$ collides elastically with $B$ as shown. If both balls have the same mass, what is the final velocity of ball $A$ ? ................$m/s$

In an elastic collision of two billiard balls which of the following quantities is not conserved during the short time of collision

A sphere $P$ of mass $m$ and moving with velocity $v$ undergoes an oblique and perfectly elastic collision with an identical sphere $Q$ initially at rest. The angle $\theta $ between the velocities of the spheres after the collision shall be ............... $^o$

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 .......... $\mathrm{m}$