Question

A wire is stretched 1 mm by applying a force of 1 KN. How far a wire of same material and the length but of 3 times diameter can be stretched?

(a) \(\frac{1}{2} \)

(b) \(\frac{1}{32} \)

(c) \(\frac{1}{16} \)

(d) \(\frac{1}{9} \)

This question was posed to me in class test.

This question is from Strength of Materials in section Strength of Materials and Construction Materials of Farm Machinery

Answer 1

Right option is (d) \(\frac{1}{9} \)

Easiest explanation: Elongation is inversely proportional to the cross-sectional area

∆l = 1 * \((\frac{1}{3})^2=\frac{1}{9}\)mm