The angle of twist of a circular shaft under a torsional moment T is given by:
Try it first: pick an option, then read the explanation.
Correct answer: B. TL/(GJ)
Asked in SSC JE 2013
Detailed Explanation
Rearrange the torsion equation for θ.
\[ \frac{T}{J} = \frac{G\theta}{L} \;\Rightarrow\; \theta = \frac{TL}{GJ} \]
Why “TL/(GJ)” Is Correct
The angle of twist is TL/(GJ) radians.
Why the Other Options Are Wrong
- A. GJ/(TL): This is the reciprocal of θ.
- C. TJ/(GL): J belongs in the denominator.
- D. TG/(JL): G must be in the denominator and L in the numerator.
Key Point
θ = TL/GJ — analogous to axial δ = PL/AE.
Key Concepts for Students
- Twist ∝ length and torque.
- Twist ∝ 1/d⁴ for a solid shaft.
- Result is in radians.
Practice more: this is question 20 in Torsion MCQs – Part 2. Try the whole set and check every answer instantly.