Q 11-12-128JEE MainJEE Main 2020 (3 Sep, Shift 1)Easy
Consider a gas of triatomic molecules. The molecules are assumed to be triangular and made of massless rigid rods whose vertices are occupied by atoms. The internal energy of a mole of the gas at temperature $T$ is:
Answer: (D) $3RT$
A rigid non-linear molecule has $3$ translational and $3$ rotational degrees of freedom, $f = 6$.
$$U = \frac f2RT = 3RT$$
Solution by Sreeraj P, M.Sc Physics