Physics · Mechanical Properties Of Solids · NEET
This is the most common confusion. In everyday language, 'elastic' means stretchy. In physics, 'more elastic' means the material resists deformation more and restores its shape with greater force — measured by Young's modulus Y = stress/strain. Rubber stretches a lot for a small force, so its strain is huge and its Y is small (about 0.01-0.1 GPa). Steel needs a very large force to stretch even a little, so its Y is very large (about 200 GPa). A bigger Y means more elastic. So steel wins.
A material is more elastic if it has a larger Young's modulus. For the same applied stress, the more elastic material shows a smaller strain (less deformation) and pushes back harder to regain its original shape. Steel's Y is roughly 1000-2000 times larger than rubber's, so steel is far more elastic. Do not judge elasticity by how far something stretches.
It comes from the internal structure. Steel is a crystalline metal with strong metallic bonds arranged in a fixed lattice, so its atoms strongly resist being pulled apart. Rubber (an elastomer) is made of long, coiled, tangled polymer chains that easily uncoil when pulled, giving very little restoring force. Strong bonds means high Y; loose coiled chains means low Y.
The rubber stretches far more. Strain = stress / Y, so for equal stress the material with the smaller Y (rubber) has the larger strain. But 'stretches more' means less elastic in physics, not more. Steel stretches only a tiny amount, showing it is the more elastic material.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Steel is more elastic because its Young's modulus (about 200 GPa) is far larger than rubber's (about 0.01-0.1 GPa). More elastic means it resists deformation more and restores its shape with a larger force.
No. In physics, more elastic means a larger Young's modulus, which gives a smaller strain for the same stress. The material that stretches more (rubber) is actually less elastic.
Steel has strong metallic bonds in a fixed crystal lattice, giving a large restoring force. Rubber has long coiled polymer chains that uncoil easily, giving a small restoring force and a small Young's modulus.
Steel shows much less strain, because strain = stress / Y and steel's Y is much larger. Smaller strain for the same stress is the sign of a more elastic material.
More elastic. Young's modulus directly measures elasticity: the higher the Y, the more the material resists deformation and the stronger it returns to its original shape.
