Difference between rigid body mechanic , deformable
body mechanic and theid mechanics?

A rigid body is one for which all the parts maintain the same positions relative to one another. I cannot deform or change shape in any way. It can only translate and rotate. It is an idealization. There is no such thing as a perfectly rigid body.

A deformable body is one that can distort. It would normally refer to a solid object so that as it deforms, it sort of deforms in a way that it could return to its starting shape if all the external forces were removed that caused it to deform. I don’t think of a blob liquid as being a deformable body even though a liquid can clearly deform. An object made of rubber is the idea that I have in mind for a deformable body.

Explanation: