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MHT CET · Physics · Mechanical Properties of Fluids

What should be the radius of water drop so that excess pressure inside it is \(72 \mathrm{Nm}^{-2}\) ? (The surface tension of water \(7.2 \times 10^{-2} \mathrm{Nm}^{-1}\) )

  1. A \(1 \mathrm{~mm}\)
  2. B \(2 \mathrm{~mm}\)
  3. C \(8\mathrm{~mm}\)
  4. D \(4 \mathrm{~mm}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(2 \mathrm{~mm}\)

Step-by-step Solution

Detailed explanation

Excess pressure in a water drop \(=\frac{2 T}{R}\)
\(
\begin{aligned}
& \mathrm{T}=7.2 \times 10^{-2} \mathrm{Nm}^{-2} \\
& \therefore 72=\frac{2 \times 7.2 \times 10^{-2}}{\mathrm{R}} \\
& \therefore \mathrm{R}=\frac{2 \times 7.2 \times 10^{-2}}{72}=2 \times 10^{-3} \mathrm{~m}=2 \mathrm{~mm}
\end{aligned}
\)
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