Question

A wire elongates by $l$ mm when a load $w$ is hanged from it. If the wire goes over a pulley and two weights $w$ each one hung at the two ends, the elongation of the wire will be (in mm)

• A. $l$
• B. $2l$
• C. zero
• D. $l/2$

Answer 1

The correct option is A $l$

$\text{Let length of wire}=L$

$\begin{array}{cc}\Delta l& =\frac{Fl}{AY}\\ l& =\frac{\omega L}{AY}\end{array}$

$\Delta l^{\prime }=\frac{Fl}{Ay}=\frac{\omega L}{Ay}=l$ Therefere elongation $=l$