1. What determines the temperature of a gas?

   The temperature of a gas is related to the average random kinetic energy of its molecules.

   For an ideal gas,

   $$\text{Average kinetic energy per molecule} = \frac{3}{2}kT$$

   where $k$ is Boltzmann's constant and $T$ is the absolute temperature.

2. Effect of uniform motion of the lorry

   The lorry is moving with uniform speed, which means there is no acceleration.

   All the gas molecules along with the container have the same additional bulk velocity due to the motion of the lorry. This is just the motion of the whole system as a whole.

3. Bulk motion vs random motion

   Temperature depends on the random motion of molecules relative to the center of mass of the gas, not on the common bulk motion of the entire container.

   If the container moves with velocity $v$, then every molecule gets that same extra velocity component. This changes the total kinetic energy seen from the ground frame, but it does not change the internal kinetic energy responsible for temperature.

4. Conclusion

   Since the lorry moves with uniform speed, there is no change in the random kinetic energy of the gas molecules.

   Therefore, the temperature of the gas molecules will remain the same.

5. Option check

   • A: increase — Incorrect
   • B: decrease — Incorrect
   • C: remain same — Correct
   • D: decrease for some, while increase for others — Incorrect

Hence, the correct answer is:

Comparison with stored correct answer: Stored answer is C, which matches the derived answer.