In an inelastic collision,after collision the kinetic energy

$A$ rubber ball is dropped from a height of $5 \ m$ on a planet where the acceleration due to gravity is unknown. After bouncing,the ball reaches a height of $1.8 \ m$. What fraction of its velocity does the ball lose upon impact?

Two particles of masses $m_1$ and $m_2$ move with initial velocities $u_1$ and $u_2$. On collision,one of the particles gets excited to a higher level after absorbing energy $\varepsilon$. If the final velocities of the particles are $v_1$ and $v_2$,then we must have:

$A$ sphere of mass $m$ moving with velocity $u$ collides with another sphere of the same mass $m$ at rest. If the coefficient of restitution is $e = \frac{1}{2}$, what is the ratio of their velocities after the collision?

$A$ ball moving with a velocity of $6\, m/s$ strikes an identical stationary ball. After collision,each ball moves at an angle of $30^{\circ}$ with the original line of motion. What are the speeds of the balls after the collision?

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 directions,collide head-on. After the collision,$A$ moves with a speed of $1 \ m/s$ in the same direction. The coefficient of restitution is: