Question

Two identical wires are suspended from a roof, but one is of copper and other is of iron. Young's modulus of iron is thrice that of copper. The weights to be added on copper and iron wires so that the ends are on the same level must be in the ratio of

• A. 1 : 3
• B. 2 : 1
• C. 3 : 1
• D. 4 : 1

Answer 1

The correct option is A 1 : 3

We know that $\Delta l=\frac{FL}{AY}$. Thus, for same length and same length, extension is inversely proportional to Y and directly proportional to force, or $\frac{F}{Y}$
Thus, for $Y$ in ratio $3:1$ for iron and copper respectively, extension will be in ratio $1:1$ only if Forces are in ratio $1:3.$