System of Particles and Rotational Motion- Notes

Rigid Body
A rigid body is a ‘system of particles’ with a finite size that do not get deformed under the influence of any external force.
The distance between ant two particles of an ideal rigid body does not change even when it is under the influence of external forces.
The motion of a rigid body, in which the velocity of all the constituent particles is the same at any instant of time, is known as ‘Translational Motion’.
This fixed line about which a rigid body rotates is called the ‘Axis of Rotation’.
When a rigid body is in rotational motion, every point on it moves along a circular path with its centre on the axis of rotation and the plane of this circle perpendicular to the axis of rotation.
The motion of any rolling body is a combination of rotational and translational motions.
If a rigid body is fixed to an axis or point, it will have pure rotational motion.

Center of mass
The center of a mass of system of particles is a point in space, whose location depends on the locations of constituent particles and their masses.