Surface tension Formula

Surface tension Formula

Surface tension is defined as the ratio of the surface force F applied on a liquid to the length d along which the force acts. It is responsible for insects to walk on water, or a paperclip to "float". The equation is given by:

Surface tension = (surface force)/(length force acts)

The equation is

γ = F /d

We have:

γ: Surface tension

F: Force applied on the liquid

d: length where the force acts

Surface tension equation Questions:

1) A small piece of metal of 1cm long weights 0.1 N, what is the surface tension?

Answer: The surface tension is calculated using the formula,

γ = F/d

γ = 0.1N/1 cm = 0.1 N/ 0.01 m = 10 N/m.

2) If the surface tension is measured to be 5 N/m, and a small insect of about 1.5 cm long is posed on the water. What is the approximate mass of the insect?

Answer: From the surface tension is found the force, which in this case is the weight:

F = γ d

F = 5 N/m * 1.5 cm = 5 N/m * 0.015 m = 0.075 N

Then the mass of the insect is given by,

M = F/g

Where g = 9.8 m/s2 is the acceleration of gravity.


M = 0.075 N / 9.8 m/s2 = 0.0076 Kg = 7.6 grams

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