Question

How much force is required to produce an increase of $0.2\%$ in the length of a brass wire of diameter $0.6mm$? (Young's modulus for brass $=0.9\times {10}^{11}N/m^2$)

• A. Nearly $17N$
• B. Nearly $34N$
• C. Nearly $51N$
• D. Nearly $68N$

Answer 1

Answer: (C)

Nearly $51N$

From Young's modulus relation,

$Y=\frac{F/A}{\Delta L/L}$

$⟹F=YA\left(\frac{\Delta L}{L}\right)$

$=0.9\times {10}^{11}\times \pi (0.0003{)}^2\times 0.002=50.8N\approx 51N$