The internal energy of a monoatomic gas is 3 nRT. One mole of helium is kept in a cylinder having internal cross section area of 17 cm^2 and fitted…

The internal energy of a monoatomic gas is $\displaystyle 3$ nRT . One mole of helium is kept in a cylinder having internal cross section area of $\displaystyle 17 \mathrm{~cm}^2$ and fitted with a light movable frictionless piston. The gas is heated slowly by suppling $\displaystyle 126$ J heat. If the temperature rises by $\displaystyle 4$ °C, then the piston will move $\displaystyle \_\_\_\_$ cm. (atmospheric pressure $\displaystyle =10^5 \mathrm{~Pa}$ )