The stress- strain graphs for two materials A and B are shown in Fig. (The graphs are to the same scale).
(i)Which of the materials has greater Young.s modulus ?
(ii) Which of the two is the stronger material ?

Explanation

(i) Young.s modulus = stress /strain = slope of the straight portion of the stress- strain graph. Since ` tan theta_(A) gt tan theta_(B) , ` slope of `OP. gt ` slope of `OP^(1)` . Y is more for material- A than that of material B.
(ii) Strength of a material is determined by the highest point on the stress- strain curve. The stress corresponding to this point is called the ultimate strength `(S_(u))`. Since this point (C ) for material- A is higher than corresponding point `(C^(1))` for material- B, `(S_(u))_(A) gt (S_(u))_(B)`. Hence, material- A is stronger than material- B.