Question

A rectangular frame is to be suspended symmetrically by two strings of equal length on two supports (Fig.) It can be done in one of the following three ways;

The tension in the strings will be

• A. the same in all cases
• B. least in (i)
• C. least in (ii)
• D. least in (iii)

Answer 1

Answer: (C)

Let $m$ be the mass of rectangular frame and $\theta$ be the angle which the tension $T$ in the string make with the horizontal from figure. Then,
$2T\sin \theta =mg$
Or $T=\frac{mg}{2\sin \theta }$
or $T\propto \frac{1}{\sin \theta }$
$T$ is least if $\sin \theta$ has maximum value
i.e., $\sin \theta =1=90^{\circ }$ or $\theta =90^{\circ }$