I=△m;r; -the moment of inertia or rotational inertia(转动惯量) on the axis Then, Inet=Ia N-Il Law for Rotation(p244) Net torque on a rigid body equals to the product of rotational inertia and angular acceleration it causes about same axis—— the moment of inertia or rotational inertia (转动惯量) on the axis. =  2 i i I m r Then,  net = I N-II Law for Rotation(p244) —— Net torque on a rigid body equals to the product of rotational inertia and angular acceleration it causes about same axis