What do you understand by the perfectly elastic, plastic, and rigid bodies? Discuss their limits.
Perfectly elastic bodies: Those bodies which regain their original configuration immediately and completely after the removal of deforming force are called perfectly elastic bodies.
Perfectly plastic bodies: Bodies which do not regain their original configuration at all on the removal of deforming forces are called perfectly plastic bodies. Generally, nobody is perfectly elastic and perfectly plastic; but they are between these two extremes. Normally, quartz is the perfectly elastic body and putty, the wax is perfectly plastic bodies.
Rigid bodies: Bodies which do not get deformed or have very small deformation on applying external force are called rigid bodies.