Q. A wire whose cross-section is 4 $mm^{2}\ $is stretched by 0.1 mm by a certain weight. How far will a wire of the same material and length stretch if its cross-sectional area is 8 $mm^{2}$ and the same weight is attached ?
A) 0.1 mm
B) 0.05 mm
C) 0.025 mm
D) 0.012 mm
Explanation
(b) $Y = \frac{Fl}{A\mathrm{\Delta}l}\ $
$Y,\ F\ and\ l\ are\ constants.$
$\therefore\ \frac{\mathrm{\Delta}l_{2}}{\mathrm{\Delta}_{1}} = \frac{a_{1}}{a_{2}} = \frac{4}{8} = \frac{1}{2}$
Or $\mathrm{\Delta}l_{2}\ \ = \frac{\mathrm{\Delta}l_{1}}{2} = \frac{0.1}{2}mm = 0.5\ mm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.