The height in terms of radius of the earth $(R)$, at which the acceleration due to gravity becomes $\frac{g}{9}$, where $g$ is acceleration due to gravity on earth's surface, is

$\_\_\_\_$ .

A metal string $A$ is suspended from a rigid support and its free end is attached to a block of mass $M$. Second block having mass 2 M is suspended at the bottom of the first block using a string $B$. The area of cross sections of strings $A$ and $B$ are same. The ratio of lengths of strings of $A$ to B is 2 and the ratio of their Young's moduli $\left(Y_A / Y_B\right)$ is 0.5 . The ratio of elongations in $A$ to $B$ is $\_\_\_\_$ .

A water spray gun is attached to a hose of cross sectional area $30 \mathrm{~cm}^2$. The gun comprises of 10 perforations each of cross sectional area of $15 \mathrm{~mm}^2$. If the water flows in the hose with the speed of $50 \mathrm{~cm} / \mathrm{s}$, calculate the speed at which the water flows out from each perforation. (Neglect any edge effects)

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A : If the average kinetic energy of $\mathrm{H}_2$ and $\mathrm{O}_2$ molecules, kept in two different sized containers are same, then their temperatures will be same.

Reason R : The r.m.s speed of $\mathrm{H}_2$ and $\mathrm{O}_2$ molecules are same at same temperature.

Choose the correct answer from the options given below