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) ?
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) ?
Updated On: Jun 24, 2024
- 125 N
- 95 N
- 115 N
- 105 N
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The Correct Option is C
Solution and Explanation
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
\(F = \frac{2AT}{d} = \frac{2\times\pi\times\left(0.05\right)^{2} \times73 \times10^{-3}}{0.01 \times10^{-3} }\)
\(= 36.5 \pi \approx 115\) newton
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Concepts Used:
Surface Tension
The amount of energy required to increase the liquid's surface area by one unit area is known as surface tension. In other words, it is a property of the liquid surface to resist force.
Surface tension is defined as,
The ratio of the surface force F to the length L along which the force acts.
Mathematically, the surface tension formula can be expressed as follows:
T=F/L
Where,
- F is the force per unit length
- L is the length in which force act
- T is the surface tension of the liquid
Read More: Detergents and Surface Tension
Factors affecting surface tension:
- Impurities: The surface tension decreases with the addition of impurities.
- Surfactants: Adding surfactants in liquids lowers the tension of water making it interrupt aside or get susceptible.
- Temperature: The surface tension of a liquid reduces as the temperature rises.
The Unit of Surface Tension:
The SI unit of Surface Tension is Newton per Meter or N/m.