Answer : Option AExplaination / Solution:
A perfectly rigid body is hypothetical in nature but for some phenomena ( in rotational bodies ) we assume bodies are perfectly rigid i.e. the intermolecular forces are always in equilibrium irrespective of the external forces due to which their shape and size are constant.
Q2.Elasticity is the property of a body, by virtue of which
Answer : Option CExplaination / Solution:
When external force is applied on the solid bodies, the solid bodies get deformed. The atoms or molecules are displaced from their equilibrium positions causing a change in the interatomic ( or intermolicular ) distances. When the deforming foce is removed, the interatomic forces tend to drive them back to their original postions. Thus the body regains its original shape and size.
Q3.The importance of the elastic behavior of materials is
Answer : Option DExplaination / Solution:
More the elastic a material is , more it has the property to regain its original position which is required in construction works.
Answer : Option AExplaination / Solution:
External force permanently distubed the equilibrium position of the interatomic ( or intermolecular ) forces between the particles of solid bodies.