Question

A thin liquid film formed between a $U$ -shaped wire and a light slider supports a weight of $1.5\times 10^{- 2}N$ . The length of the slider is $30cm$ and its weight is negligible. The surface tension of the liquid film is :

• A. $0.0125Nm^{- 1}$
• B. $0.1Nm^{- 1}$
• C. $0.05Nm^{- 1}$
• D. $0.025Nm^{- 1}$

Answer 1

Answer: (D)

$2Tl=W$
$T=\frac{W}{2 l}=\frac{1 . 5 \times 10^{- 2}}{2 \times 0 . 3}$
$=2.5\times 10^{- 2}Nm^{- 1}$