Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Well, the question says it all; is there a definition of body in physics? What is to be considered a physical object and what it cannot?

share|improve this question

2 Answers 2

There is no general definition of a body for physics, as in everyday speech where one has to qualify further either by context or content.

A body of water, means a bulk ensemble of water molecules and further analysis depends on the context.

Two colliding bodies could be billiard balls or asteroids. It is a blanket term that needs further attributes if it is to be used in a problem that needs a mathematical solution in physics.

share|improve this answer

If you are talking about rigid bodies like billiard balls or asteroids one has a definition of a body:

In physics, a rigid body is an idealization of a solid body in which deformation is neglected. In other words, the distance between any two given points of a rigid body remains constant in time regardless of external forces exerted on it.(Wikipedia)

However this seem a little bit fishy since it also uses the word “body” in its definition. However one can also define a body in Classical Mechanics as a collection of atoms (or just one atom for that matter) having a well-defined energy, velocity, mass and momentum. Things get a little complicated when you are dealing with QM.

To answer your second question: You can think of anything as physical object so long as you obey the above-mentioned rules. E.g. a body with infinite mass is not a physical object, it is just an idealisation of a very heavy physical object.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.