Degrees Of Freedom
For diatomic gas at moderate temperature (rotations active, vibrations inactive) f =:
Select the correct option:
Solution
5
The number of degrees of freedom (f) is the number of independent ways a molecule can possess energy.
- Translational: All gas molecules have 3 translational degrees of freedom (x,y,z directions).
- Rotational: A linear diatomic molecule (like H2,O2,N2) can rotate about two axes perpendicular to the bond axis. Rotation about the bond axis itself has negligible moment of inertia and doesn't contribute at moderate temperatures.
- Total f = 3 (trans) + 2 (rot) = 5. Note: At very high temperatures, 2 vibrational degrees of freedom may also activate.
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About This Question
- Subject
- physics
- Chapter
- kinetic theory of gases
- Topic
- degrees of freedom
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
5
The number of degrees of freedom (f) is the number of independent ways a molecule can possess energy.
- Translational: All gas molecules have 3 translational degrees of freedom (x,y,z directions).
- Rotational: A linear diatomic molecule (like H2,O2,N2) can rotate about two axes perpendicular to the bond axis. Rotation about the bond axis itself has negligible moment of inertia and doesn't contribute at moderate temperatures.
- Total f = 3 (trans) + 2 (rot) = 5. Note: At very high temperatures, 2 vibrational degrees of freedom may also activate.
This medium difficulty physics question is from the chapter kinetic theory of gases, covering the topic of degrees of freedom. It appeared in the 2025 exam.
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