Question

The maximum elongation of a steel wire of 1m length if the elastic limit of steel and its Young’s modulus, respectively, are 8 × \(10^8\) N \(m^{–2}\) and 2 × \(10^{11}\) N \(m^{–2}\) is: 

(1) 4 mm 

(2) 0.4 mm 

(3) 40 mm 

(4) 8 mm

Answer 1

Correct option is : (1) 4 mm

\( Y = \frac{Fl}{A\Delta l}\) 

\(\Delta l = \frac{(\frac{F}{A})l}{Y}\)

\(\Delta l = \frac{8\times10^8\times1}{2\times10^{11}}\)

\(\Delta l = 4mm\)