$A$ ball is dropped from a height $h$. After it strikes the ground twice,what height will it reach?

$A$ ball moving with a velocity of $9 \ m/s$ collides with another similar stationary ball. After the collision,both balls move in directions making an angle of $30^{\circ}$ with the initial direction. After the collision,their speed will be $-$

$A$ ball kept at $20 \,m$ height falls freely in a downward direction vertically and hits the ground. The coefficient of restitution is $0.4$. After the first rebound, the upward velocity is $[g = 10 \,m/s^2]$. (in $\,m/s$)

$A$ $2 \,kg$ ball moving at $24 \,ms^{-1}$ undergoes inelastic head-on collision with a $4 \,kg$ ball moving in the opposite direction at $48 \,ms^{-1}$. If the coefficient of restitution is $2/3$, their velocities in $ms^{-1}$ after impact are

$A$ body of mass $m_1$ moving with a velocity $3 \, ms^{-1}$ collides with another body at rest of mass $m_2$. After the collision,the velocities of the two bodies are $2 \, ms^{-1}$ and $5 \, ms^{-1}$ respectively along the direction of motion of $m_1$. The ratio $\frac{m_1}{m_2}$ is:

$A$ ball $P$ of mass $0.5 \ kg$ moving with a velocity of $10 \ ms^{-1}$ collides with another ball $Q$ of mass $1 \ kg$ at rest. If the coefficient of restitution is $0.4$,the ratio of the velocities of the balls $P$ and $Q$ after the collision is