As an example, if you had a tube that was being twisted, the cross-sectional area needed for the calculation would be the area of the circular cross-section of the tube. The twisting of an object will happen around the axis from where to calculate the polar moment of inertia. How Do You Calculate the Polar Moment of Inertia?
Rectangular Cross Section Polar Moment of Inertia.Square Cross Section Polar Moment of Inertia.
Hollow Circular Cross Section Polar Moment of Inertia.Solid Circular Cross Section Polar Moment of Inertia.How Do You Calculate the Polar Moment of Inertia?.