5.5 Rotational Equilibrium and Newton’s First Law in Rotational Form

Newton’s First Law (Rotational Form)

Newton’s First Law states: an object at rest remains at rest, and an object in motion remains in uniform motion unless acted upon by a net external force.

The rotational analogue is: A rigid body at rest will remain at rest, and a rotating body will continue rotating with a constant angular velocity unless acted upon by a net external torque.

When the net torque acting on a rigid body is zero, the body is in rotational equilibrium.

Important Equation: ${\tau_{net} = 0}$

This means angular velocity (${\omega}$) remains constant, just as linear velocity remains constant when ${F_{net} = 0}$.