greetings, in kinematics branch of physics, what is the difference between a particle and body? i have read that a particle is a point object without an extend but i did not get the idea. although, particle generally refers to atom or molecules in chemistry, i don’t get the difference in physics. please explain it.

Kinematics is the study of the motion of points, objects, and groups of objects without considering the causes of its motion.

Concept of a Point Object:

A real object can rotate as it moves.

For example,
a cricket ball may be spinning while it is moving, as a whole, in a trajectory. Also, a body may vibrate as it moves, for example, a falling water droplet. These complications can be avoided by considering the motion of a very small body called a particle or a point object. Mathematically, a particle is treated as a point, an object without extension, so that rotational and vibrational motions are not involved.Actually, there is no such thing in nature as an object without extension. The concept of a particle or a point object is very useful because real objects often behave to a great extent, like particles. A body need not be 'small' in the usual sense of the word, in order to be treated as a particle. For example, if we consider the distance from the Earth to the sun, with respect to the distance between them, both the Earth and the sun can be treated as particles or point objects.


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