Question

A wire elongates by 1.0 mm when a load W is hanged from it. If this wire goes over a pulley and two weights W each are hung at the two ends, the elongation of the wire will be

• A. $0.5m$
• B. $1.0m$
• C. $2.0mm$
• D. $4.0mm$

Answer 1

The correct option is B $1.0m$

Elongation in the wire $\infty$ Tension in the wire
In first case $T_1$ = W and in second case $T_2$ = $\frac{2W\times W}{W+W}$ = W
As $\frac{T_1}{T_2}=1$ $\therefore$ $\frac{l_1}{l_2}=1$ $\Rightarrow$ $l_2=l_1=1.0mm$