Which one of these is more elastic, steel or rubber ? Why ?

Explanation

(i) We know that young's modulus is the ratio of stress to the strain. If the same force is applied to the wire of steel and rubber thread, which are of equal length and cross section area, we will find that the extension in the rubber thread is much greater than extension in steel wire.
(ii) Therefore, for a given stress, the strain produced in steel is much smaller than that produced in the rubber. THis implies that young's modulus for steel is greater than that for rubber. Therefore, steel is more elastic than rubber.
Young's modulus of steel, `Y, = (F)/(A) (I)/(Delta I_(s))`
Young's modulus of rubber, `Y, = (F)/(A) (I)/(Delta I_(r ))`
(iii) For same force applied to wires made of steel & rubber of same length and same area of cross section `Delta I_(s) lt Delta I_(r )`
`(Y_(s))/(Y_(r )) = (Delta I_(r ))/(DeltaI_(s)) gt 1`
`:. Y_(s) gt Y_(r )`