A merry-go-round rotating at a constant angular speed completes 9 rotations is 18 s . What is its angular speed?

A motor car moving with velocity $7 \mathrm{~m} / \mathrm{s}$ stops at 10 m distance when brakes are applied. What is the relation between the resistance force $R$ and the weight $w$ of the car? (take, value of $g=9.8 \mathrm{~m} / \mathrm{s}^2$ )

A ball of mass 1 kg moves in a straight line with velocity $v=c x^\alpha$, where $c=1$ (SI unit) and $\alpha$ is a constant. If the work done by the net force during its displacement from $x=0$ to $x=4 \mathrm{~m}$ is 128 J , then the $\alpha$ is

Assertion (A) In an elastic collision of two billiard balls, both kinetic energy and linear momentum remain conserved.

Reason (R) During the collision of the balls, as the collision is elastic there is no exchange of energy. Therefore, both energy and momentum are conserved. The correct option among the following is