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 > slope of `OP^1` . Y for material-A > Y for 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-B is higher than corresponding point`(C^1)` for material-A, `(S_u)_B gt (S_u)_A`. Hence, material B is stronger than material-A.