A block of mass $m$ slides down on a smooth parabolic surface from height $h$ as shown. Find its speed at lowermost position

A block of mass $m$ is released from a height $R$ on the frictionless incline as shown. The incline leads to a circle of radius $\frac{R}{2}.$ The maximum height attained by the block is

In the spring mass system shown in the figure, the spring is compressed by $x_0=\frac{mg}{3k}$ from its natural length and the block is released from rest. The speed of the block, when it passes through the point $P$ at means position, is

Five identical balls each of mass $m$ are placed adjacent to each other at rest on a smooth horizontal floor. An another identical ball moving with speed $v$ collides elastically with the left most ball as shown in figure. After collision(s)