If the torque on a shaft doubles, the required diameter increases by approximately what factor according to the diameter formula?

Study for the NANTeL Mechanical Engineering Certification Test. Master the format with quizzes, hints, and explanations designed for exam success. Ready yourself with focused preparation for your certification!

Multiple Choice

If the torque on a shaft doubles, the required diameter increases by approximately what factor according to the diameter formula?

Explanation:
In torsion of a solid circular shaft, the torque is related to the diameter by T ∝ d^3 when the allowable shear stress is fixed. The exact relation is T = (τ π d^3)/16, so solving for diameter gives d = [16 T / (π τ)]^(1/3). This shows diameter depends on the cube root of torque. If the torque doubles, the new diameter becomes d' = [16 (2T) / (π τ)]^(1/3) = 2^(1/3) d. Therefore the required diameter increases by a factor of 2^(1/3) ≈ 1.26. The other factors (2, 1, or 1.414) correspond to different power relationships and don’t apply here.

In torsion of a solid circular shaft, the torque is related to the diameter by T ∝ d^3 when the allowable shear stress is fixed. The exact relation is T = (τ π d^3)/16, so solving for diameter gives d = [16 T / (π τ)]^(1/3). This shows diameter depends on the cube root of torque. If the torque doubles, the new diameter becomes d' = [16 (2T) / (π τ)]^(1/3) = 2^(1/3) d. Therefore the required diameter increases by a factor of 2^(1/3) ≈ 1.26. The other factors (2, 1, or 1.414) correspond to different power relationships and don’t apply here.

Subscribe

Get the latest from Passetra

You can unsubscribe at any time. Read our privacy policy