NEET · Physics · STD 11 - 9.2 surface tension
A thin flat circular disc of radius \(4.5 \mathrm{~cm}\) is placed gently over the surface of water. If surface tension of water is \(0.07 \mathrm{~N} \mathrm{~m}^{-1}\), then the excess force required to take it away from the surface is
- A \(198 \mathrm{~N}\)
- B \(1.98 \mathrm{mN}\)
- C \(99 \mathrm{~N}\)
- D \(19.8 \mathrm{mN}\)
Answer & Solution
Correct Answer
(D) \(19.8 \mathrm{mN}\)
Step-by-step Solution
Detailed explanation
\(\text { Excess force }=T \times 2 \pi R\) \(=\frac{7}{100} \times 2 \times 3.14 \times \frac{4.5}{100}\)
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