Physics · Mechanical Properties Of Solids · NEET
Yes. Rubber is the classic elastomer. NCERT says rubber can be pulled to several times its original length and still returns to its original shape once you let go. Returning to original shape means it IS elastic. So an elastomer is elastic, it just has a very large elastic region.
No, not over most of the region. Hooke's law needs stress to stay directly proportional to strain (a straight-line graph). NCERT clearly states that although the elastic region of an elastomer like aorta tissue is very large, the material does not obey Hooke's law over most of it. So the stress-strain graph of an elastomer is a curve.
They are elastic. A plastic material keeps a permanent change after the force is removed. An elastomer goes back to its original shape, so it is elastic, not plastic. The confusion comes from the huge stretch, but huge stretch that fully recovers is still elastic behaviour.
Very low. NCERT states metals have larger Young's modulus than alloys and elastomers. A large Young's modulus means a large force is needed for a small length change. Elastomers stretch a lot for a small force, so their Young's modulus is small. This is why steel (high Young's modulus) is called more elastic than rubber.
Both return to original shape, so both are elastic. Steel obeys Hooke's law up to its elastic limit and gives a straight-line graph with a high Young's modulus. An elastomer has a very large elastic region, does not follow the straight line (no Hooke's law), and has a low Young's modulus. Example of an elastomer: rubber, aorta tissue.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A material that can be stretched to several times its original length and still return to its original shape, but does not obey Hooke's law over most of that region. Rubber is the standard example.
Rubber and the elastic tissue of the aorta (a part of the heart). NCERT uses the aorta stress-strain curve to show elastomer behaviour.
Because stress is not proportional to strain for an elastomer over most of the region. Hooke's law (straight line) fails, so the graph bends. The graph also does not retrace the same path on loading and unloading, showing elastic hysteresis.
Low. NCERT states metals have larger Young's modulus than alloys and elastomers. Low Young's modulus means a small force causes a large stretch, which is exactly what rubber does.
No. A plastic keeps a permanent change after the force is removed. An elastomer returns to its original shape, so it is elastic, not plastic.
