Q. A uniform wire, fixed at its upper end, hangs vertically and supports a weight at its lower end. If its radius is r, its length L and the Young’s modulus for the material of the wire is E, the extension is 1. directly proportional to E 2. inversely proportional to r 3. directly proportional to L
A) If only 3 is correct
B) If 1, 2 are correct
C) If 2, 3 are correct
D) If only 1 correct
Explanation
(a) $E = \ \frac{FL}{\pi r^{2}\mathrm{\Delta}L}\ or\ \mathrm{\Delta}L = \frac{FL}{\pi r^{2}E}\ $
Clearly , $\mathrm{\Delta}L\ \propto L$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.