MECHANICAL PROPERTIES OF SOLIDS
RIGID BODY A rigid body means a body which its ralative position of the constituent particles does not change when an external force is applied on it. A rigid body generally have a definite shape and size. In case of solid, it can be deformed when a sufficiently large external force is applied on it; i.,e., solid bodies are not perfectly rigid an also in practice, no body is perfectly rigid. ELASTICITY The property of a body which tends to regain its original size and shape, when the external applied force is removed is known as elasticity. In a solid, the constituent paricles like atoms or molecules have thier definite ralative positions due to its interatomic or intermolecular forces, that means they are in a stable equilibrium position. When the solid is under the action of an external applied force, the atoms or molecules are displaced from thier equilibrium positions. If the external force or the deforming force is removed, these atoms or molecules start to back t...