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 ?

The stress- strain graphs for two materials A and B are shown in Fig.

1.	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 ?
Answer» Solution : 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.