A monoatomic gas of mass 4.0 u is kept in an insulated container. Container is moving with velocity $30 \mathrm{~m} / \mathrm{s}$. If container is suddenly stopped then change in temperature of the gas $\left(R=\right.$ gas constant) is $\frac{x}{3 R}$. Value of $x$ is $\_\_\_\_$ .
