MHT CET · Physics · Mechanical Properties of Fluids
Two glass plates of area \(10^{-2} \mathrm{~m}^2\) have \(10 \mathrm{~cm}\) thick water film between them. The surface tension of water is \(70 \times 10^{-3} \mathrm{~N} / \mathrm{m}\). The force required to separate two glass plates from each other is
- A 14 N
- B 17 N
- C 28 N
- D 30 N
Answer & Solution
Correct Answer
(A) 14 N
Step-by-step Solution
Detailed explanation
Consider complete wetting.
The Laplace pressure jump is given by:
\(\begin{aligned}
& \Delta P=\frac{\sigma}{\left(\frac{h}{2}\right)}=\frac{F}{A} \\
& \Rightarrow F=\frac{A \sigma}{\frac{h}{2}}=\frac{10^{-2} \times 70 \times 10^{-3}}{5 \times 10^{-2}} N=28 \mathrm{~N}
\end{aligned}\)
The Laplace pressure jump is given by:
\(\begin{aligned}
& \Delta P=\frac{\sigma}{\left(\frac{h}{2}\right)}=\frac{F}{A} \\
& \Rightarrow F=\frac{A \sigma}{\frac{h}{2}}=\frac{10^{-2} \times 70 \times 10^{-3}}{5 \times 10^{-2}} N=28 \mathrm{~N}
\end{aligned}\)
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