Topic: Elastic behaviour, stress-strain, Hooke's law, Young's, bulk and rigidity moduli· Properties of Solids and Liquids

Two wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the second wire has cross-sectional area 3A. If the length of the first wire is increased by Δ l on applying a force F, how much force is…

Two wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the second wire has cross-sectional area 3A. If the length of the first wire is increased by $\Delta l$ on applying a force F, how much force is needed to stretch the second wire by the same amount ?

1. 9 F

2. 4 F

3. 6 F

4. F

Doubtly Asked 30 Oct 2026 NEET UG 2018 Practice test neet Save WhatsApp Report

1 answer

Best answer

Answer: 1. 9 F

Same volume: $A\,l=3A\,l_2$, so the second wire has length $l_2=\dfrac l3$.

From $Y=\dfrac{F\,l}{A\,\Delta l}$, $F=\dfrac{YA\Delta l}{l}$.

$$F_2=\frac{Y(3A)\Delta l}{l/3}=9\cdot\frac{YA\Delta l}{l}=9F$$

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

Was this answer helpful?

Two wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the second wire has cross-sectional area 3A. If the length of the first wire is increased by Δ l on applying a force F, how much force is…

1 answer

Your answer