ï»¿ Define surface energy and show that surface energy is equal to surface tension. from Physics Mechanical Properties of Fluids Class 11 Manipur Board

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Define surface energy and show that surface energy is equal to surface tension.

The amount of mechanical work required to increase the unit area of aÂ free surface under the isothermal condition is known as surface energy.Â

To show: Surface energy is equal to surface tension

i) Take a wired rectangular frame whose three sides are rigid and one side AB is free to slide.

ii) Dip the frame in aÂ soap solution to form the film.

iii) The surface tension force acts on all the sides of the frame.

iv) Side AB is free to slide and the other three sides being fixed cannot displace. Due to surface tension force slides in left direction and free surface tries to contract.

Let surface tension of soap solution be T and length of movable rod AB beÂ l.

There are two free surfaces of liquid which touch the movable wire AB.

The surface tension of total inward force on the wire = 2Tl.

If frame AB is displaced by distance x in right direction, then work done against surface tension to increase the surface area is,
Â  Â  Â  Â Â
Â

Increase in surface area of film is
Â
Â  Â  Â  Â  Â  Â  Â  Â  Â  Â Â

Â  Â  Â  Â  Â  Â

Â  Â Â

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Hydrostatics is the branch of fluid mechanics that studies incompressible fluids at rest. The study of fluids at rest or objects placed at rest in fluids is hydrostatics.
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What is fluid?

Any material that can flow is a fluid. Liquids and gases are examples of fluid.

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What is hydrodynamics?

Hydrodynamics is the branch of science that studies about the force exerted by the fluids or acting on the fluids.
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Why solids have definite shape while liquids do not have definite shape?

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