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

Options

A. the same in all cases
B. least in (a)
C. least in (b)
D. least in (c)

Answer

C

Explanation

Let m be the mass of rectangular frame and `theta` be the angle which the tension T in the string make with the horizontal. Refer Fig. 7(EP).6. Then
`2T sin theta=mg`
or `T=(mg)/(2 sin theta)` or `T prop (1)/(sin theta)`
T is least it `sin theta` has maximum value i.e. `sin theta= 1= sin 90^(@)` or `theta=90^(@)`. Thus option (c) is correct.