Polar moment of inertia is a quantity used to predict an object's ability to resist
torsion, in objects (or segments of objects) with an invariant circular
cross section and no significant warping or out-of-plane deformation. It is used to calculate the
angular displacement of an object subjected to a
torque. It is analogous to the
area moment of inertia, which characterizes an object's ability to resist
bending and is required to calculate
displacement.