Question

The polar moment of inertia of the cross-section of the member is required to assess the strength of the member in

• A. bending
• B. torsion
• C. axial force
• D. shear

Answer 1

The correct option is B torsion

According to torsion formula

$\Rightarrow \frac{T}{J}=\frac{f_s}{R}$

$\Rightarrow T=f_s.Z_p$

$where,Z_p=\frac{J}{R}$

$=\frac{Polar/momentofinertia}{Maximumradius}$

$\therefore$ The greatest twisting moment which a given shaft section can resist.

= maximum permissible shear $\times$ Polar modulus

$\therefore$ Polar moment of inertial asses the strength of member in torsion