Question

A mass $m$ is hanging from a wire of cross-sectional area $A$ and length $L.Y$ is young's modulus of wire. An external force $F$ is applied on the wire which is then slowly further pulled down by $\Delta x$ from its equilibrium position. find the work done by the gravity, if $\Delta l$ is the elongation.

• A. $mg\Delta l$
• B. $mg\Delta x$
• C. $\frac{mg{\left(\Delta l\right)}^2}{\Delta x}$
• D. $\frac{mg{\left(\Delta x\right)}^2}{\Delta l}$

Answer 1

The correct option is B $mg\Delta x$

When external force is applied,
Work done by the gravity $=mg\Delta x$
Final Answer: (b)