MHT-CET : Physics Entrance Exam

### MHT - CET : Physics - Properties of Fluids Formulae Page 1

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 1. Surface Energy Surface energy = Surface tension ´ surface area

2. Rise of Liquid in a Capillary

 h = 2 T cos q , where T is the surface tension of the liquid, q r r g

 is the angle of contact, r is the radius of the capillary bore and r the density of the liquid.

3. Free Surface Energy

 For a drop, E = 4pr2T For a bubble, E = 2 ´ 4pr2T, since a bubble has two free surfaces.

4. Capillary Rise

Difference in heights in the two limbs of a U tube capillary, which is vertical, is

 a. b.

 given by, h = 2 T COsq 1 - 1 , where r1 and r2 are the radii of the two limbs of the capillary. r g r1 r2 For two different capillaries: (same liquid)     h1r1 = h2r2

 5. Total Surface Area of a Soap Bubble Total surface area of a soap bubble = 2 ´ surface area

6. Angle of Contact for Water and Glass

For water, angle of contact = q = 0° \ COsq = 1

 r = 1 gm/cc : T = hrg 2

 7. Work Done in Breaking a Liquid Drop If a liquid drop breaks into number of spherical droplets, Work done = T ´ increase in surface area

 8. Energy Released During Formation of a Liquid Drop If liquid drops coalesce to form a single drop, Decrease in surface energy = T ´ decrease in surface area

 9. Work Done in Increasing the Radius of a Soap Bubble Work done in increasing the radius of a soap bubble = T ´ 2 ´ increase in surface area

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