Question 154 of 192
A thin liquid film formed between a U-shaped wire and a light slider supports a weight of (see figure). The length of the slider is and its weight negligible. The surface tension of the liquid film is
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Answer: (D)
The force of surface tension acting on the slider balances the force due to the weight.
$\begin{array}{ll}
\Rightarrow & \mathrm{F}=2 \mathrm{~T} \ell=\mathrm{w} \\
\Rightarrow & 2 \mathrm{~T}(0.3)=1.5 \times 10^{-2} \\
\Rightarrow & \mathrm{T}=2.5 \times 10^{-2} \mathrm{~N} / \mathrm{m}
\end{array}$
$\begin{array}{ll}
\Rightarrow & \mathrm{F}=2 \mathrm{~T} \ell=\mathrm{w} \\
\Rightarrow & 2 \mathrm{~T}(0.3)=1.5 \times 10^{-2} \\
\Rightarrow & \mathrm{T}=2.5 \times 10^{-2} \mathrm{~N} / \mathrm{m}
\end{array}$
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