Moreover, a rigid body can be considered as a combination of small particles. Thus, the concepts learned for a particle can be helpful in understanding the kinematics of rigid body.

L17 : Kinematics of a Particle

Kinematics is the area of mechanics concerned with the study of motion of particles and rigid bodies without consideration of what has caused the motion. When we take into consideration the factors causing the motion, the area of study is called dynamics.

A particle has no size but has mass. This is a completely hypothetical concept. However, many times object can be approximated as particle. For example, a car is moving. Compared to distance, it travels, its size is very small and it can be treated as particle.