Civil Engineering MCQAE Level Civil Engineering
For a circular shaft, torque T=3.0 kN-m, polar moment J=2.0×10^6 mm⁴ and radius 30 mm. Maximum shear stress is
Structural AnalysisOriginal practiceMEDIUM
Choose the correct answer
A
67.5 N/mm²
B
90 N/mm²
C
22.5 N/mm²
D
45 N/mm²
Correct Answer
D. 45 N/mm²
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Torsion formula: shear stress tau = T*R/J, where T = applied torque, J = polar second moment of area (pi*D^4/32 for solid shaft), R = outer radius. Full torsion equation: tau/R = T/J = G*theta/L (G = modulus of rigidity, theta = angle of twist, L = shaft length). Valid for circular sections in elastic range. Using τ/R = T/J, τ = TR/J = 45 N/mm².
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