· A rigid body is the one in which the distances between different particles remain constant.
· For regular shaped bodies with uniform mass distribution, center of mass always lies at the geometrical center.
· Net torque produces turning motion in rigid object.
· A rigid body is in translational equilibrium if the total external force on it is zero. It is in rotational equilibrium if the total external torque on it is zero.
· The center of gravity of an extended body is that point where the total gravitational torque on the body is zero.
· If the external torque acting on the body is zero, the component of angular momentum along the axis of rotation is constant.
· There are rotational equivalents for all the translational quantities.Rolling motion is the combination of translational and rotation motions.
· Rolling can also be treated as the momentary rotation about the point of contact.
· In pure rolling, the total kinetic energy is the sum of kinetic energies of translational and rotational motions.
· In sliding the translational motion is more than rotational motion.
· In slipping the rotational motion is more than translational motion.