$A$ ball is released from a certain height. It loses $50\%$ of its kinetic energy on striking the ground. It will attain a height again equal to

$A$ ball of mass $m$ falls vertically from a height $h$ and collides with a block of equal mass $m$ moving horizontally with a velocity $v$ on a surface. The coefficient of kinetic friction between the block and the surface is $0.2$,while the coefficient of restitution $e$ between the ball and the block is $0.5$. There is no friction acting between the ball and the block. The velocity of the block decreases by:

Two balls at the same temperature collide. What is conserved?

Which one of the following statements does not hold true when two balls of masses $m_1$ and $m_2$ undergo an elastic collision?

$A$ constant power of $7 \,W$ is supplied to a toy car of mass $15 \,kg$. The distance travelled by the car when its velocity increases from $3 \,ms^{-1}$ to $5 \,ms^{-1}$ is: (in $\,m$)

An open knife edge of mass $m$ is dropped from a height $h$ on a wooden floor. If the blade penetrates up to the depth $d$ into the wood,the average resistance offered by the wood to the knife edge is