Ap Physics B Review - Fluid Dynamics

AP Phys B Test Review Fluid Mechanics 4/29/2008

Overview  Fluid

Mechanics

• Hydrostatics and Fluid Dynamics • Fluid Pressure • Pascal’s and Archimedes Principles • Continuity Equation and Bernoulli’s Equation

Overview  Thermodynamics

• Heat, Temperature, Energy • Thermal Expansion • Ideal Gas Law • PV Diagrams • Laws of Thermodynamics

Density and Pressure 

Density: How much matter is present in a given volume.

m ρ = V

• 

Specific Gravity – ratio to the density of water

Pressure: Force exerted over a given area in an object (measured in Pascals [Pa])

F P = A

Pressure Measurements  Absolute

vs. Gauge Pressure  Many different units (Pa, kPa, torr, mbar, atm….)

• Take care that units are correct when dealing •

with pressure. When in doubt, convert to Pa!

Variation of Pressure with depth 

The pressure on an object varies with the depth the object is at.

P = P0 + ρg h

Pascal’s Principle 

A change in pressure applied to an enclosed fluid is transmitted undiminished to every point in the fluid and to the walls of the container.

•

Hydraulic Press

Archimedes Principle 

An object completely or partially submerged in a fluid is buoyed up by a force with equal magnitude to the weight of the fluid displaced by the object.

•

For a floating object

ρobj

V flu id = ρ flu id V o b je c t

Equation of Continuity 

The “equation of continuity” is nothing more than an expression of the conservation of mass for a moving fluid.

A1v1 = A 2 v2 •

Av = flow rate

•

Volume entering a tube in a given time interval must be equal to the volume leaving the tube in the same time interval.

Bernoulli’s Principle  Swiftly

moving fluids exert less pressure than slowly moving fluids.