Question

Steel wire of length 5.7 m and cross-sectional area 3*10^-5 m^2 is stretched by the same amount as a Copper wire of 3.5 m length and 4*10^-5m^2 cross-sectional area, under a given load. What would be the ratio of their Young’s modulus?

(a) 2.3:1.9

(b) 1.5:1.5

(c) 1.6:1.8

(d) 2.2:1.3

This question was posed to me in final exam.

The question is from Strength of Materials topic in chapter Strength of Materials and Construction Materials of Farm Machinery

Answer 1

The correct choice is (d) 2.2:1.3

To elaborate: Y1 = \(\frac{F1.L1}{A1.l1} = \frac{F1*4.7}{3*10^{-5} l1} \)

Y2 = \(\frac{F2.L2}{A2.l2} = \frac{F2*3.5}{4*10^{-5} l1} \)

\(\frac{Y1}{Y2} = \frac{5.7*4*10^{-5}}{4.5*3*10^{-5}}\) = 2.2:1.3