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NEET 2024
Exam
NEET
Year
2024
Subject
Physics
Chapter
Mechanical Properties of Fluids

NEET 2024 · Physics · Mechanical Properties of Fluids

A thin flat circular disc of radius 4.5 cm is placed gently over...

A thin flat circular disc of radius 4.5 cm is placed gently over the surface of water. If surface tension of water is 0.07 N m−10.07 \mathrm{~N} \mathrm{~m}^{-1}, then the excess force required to take it away from the surface is

Options

  1. A198 N
  2. B1.98 mN
  3. C99 N
  4. D19.8 mN

Correct answer

D. 19.8 mN

Step-by-step solution

 Excess force =T×2πR=7100×2×3.14×4.5100=197.82×10−4=19.8×10−3N=19.8mN\begin{aligned} & \text{ Excess force }=T \times 2 \pi R \\ & =\frac{7}{100} \times 2 \times 3.14 \times \frac{4.5}{100} \\ & =197.82 \times 10^{-4} \\ & =19.8 \times 10^{-3} \mathrm{ N} \\ & =19.8 \mathrm{mN}\end{aligned}
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