Chapter 15Fluids

Dr. Haykel Abdelhamid Elabidi

1st/2nd week of December 2013/Saf 1435

Units of Chapter 15

• Density

• Pressure

• Static Equilibrium in fluids

• Archimedes' Principle and Buoyancy

• Fluid Flow and Continuity

• Bernoulli's Equation

Density

Definition of fluid: it is a substance that can readily flow from place to place, and take the shape of a container rather than retain a shape of their own.Examples: gases and liquids

Pressure

Pressure

The pressure in fluid acts equally in all directions, and acts at right angles to any surface, so we don’t usually notice it.

Pressure

Static equilibrium in fluids: Pressure and depth

The increased pressure as an object descends through a fluid is due to the increasing mass of the fluid above it.

Static equilibrium in fluids: Pressure and depth

Static equilibrium in fluids: Pressure and depth

Static equilibrium in fluids: Pressure and depth

Static equilibrium in fluids: Pressure and depth

Archimedes’ principle and buoyancy

A fluid exerts a net upward force on any object it surrounds, called the buoyant force.

the buoyant force is due to the increased pressure at the bottom of the object compared to the top.

Archimedes’ principle and buoyancy

Archimedes’ principle and buoyancy

Fluid flow and continuity

Continuity tells us that whatever the volume of fluid in a pipe passing a particular point per second, the same volume must pass every other point in a second. The fluid is not accumulating or vanishing along the way.

This means that where the pipe is narrower, the flow is faster.

Fluid flow and continuityMost gases are easily compressible; most liquids are not. Therefore, the density of a liquid may be treated as constant, but not that of a gas.

3.

Bernoulli’s equation

The Bernoulli’s Equation is the work – energy theorem applied to fluids. The result is a relation between the pressure of a fluid, its speed, and its height.

If there is no change in height, the Bernoulli’s equation becomes:

Bernoulli’s equation

Bernoulli’s equationExercise 15-4 page 520

There is a difference in height, so we apply the Bernoulli’s equation (the subscript (1) for the bottom and (2) for the top:

Bernoulli’s equation

Figure 15-19

Thank you for your attention

See you next time Inchallah