Question

Two circular plates of radius $5\, cm$ each, have a $0.01\, mm$ thick water film between them. Then what will be the force required to separate these plate (S.T. of water = $73$ dyne/cm) ?

• A. 125 N
• B. 95 N
• C. 115 N
• D. 105 N

Answer 1

Answer: (C)

115 N

Answer 2

The correct option is (C): 115 N.
$F = \frac{2AT}{d} = \frac{2\times\pi\times\left(0.05\right)^{2} \times73 \times10^{-3}}{0.01 \times10^{-3} }$
$= 36.5 \pi \approx 115$ newton