Which term describes the twisting of an object due to an applied torque?

• A. Tension
• B. Bending
• C. Torsion
• D. Compression

Answer: (C)

Torsion is the twisting of an object caused by an applied torque. When a torque acts along the axis, different layers of the material are driven to rotate by different amounts, producing a twist along the length. This twist creates shear stresses in the cross-section rather than simply pulling or pushing along the length.

This is distinct from tension, which stretches the object along its length; compression, which shortens it along its length; and bending, which curves the object because one side is pulled tight while the opposite side is pushed. In torsion, the important quantities are the torque, the length, and the material’s shear properties; the angle of twist depends on those factors as well as the polar moment of inertia of the cross-section.