Chapter 9

Pascal's Law and Bernoulli's Principle

Blaise Pascal ....................... Daniel Bernoulli

Demos to Prepare:

Capillarity:
Tubes
Liquids:  Lycopodium Powder is almost a liquid.
Surface Tension:
Surface Tension and Viscosity,  Ice in Cooking Oil in Cylinder.

Kinetic Theory:
1. Gas Pressure.  The force of molecular collisions.
A balloon expands as air is added, yet it is still compressible.  Air thermometer.
2. Heat Conduction.  From molecule to molecule the energy is transferred.
3. Evaporation.  Moving molecules escaping thru the surface tension.  Warmer evaporates faster.
4. Vapor Pressure. Force of evaporating molecules. Steam power!
5. Expansion upon heating. Moving and colliding molecules push each other farther apart.  Ball & Ring,
(The Brass Monkey.)
6. Diffusion.  The intermingling of moving molecules.
Coloring in water, NH3 gas on the loose.  50+50= 95!
7. Osmosis.  Diffusion thru a porous membrane.
Graham's Law-- The rate of diffusion is inversely
proportional to the square root of the molecular
mass. Heavy molecules diffuse more slowly.
8. Brownian Motion. Smoke & dust particles are jostled around by molecular impact. Keeps clouds up!
9. Electron microscopy photographs!

Pascal & Pressure:
High Heels
Bed of Nails
Gramophone needle
Big Tyres on Small People
Water Tanks
Manometers, Water & Mercury
Bourdon Gauges
Tower 2 & 88mm Aqua Cannon
Submarines
Bathyscaph at 10,000 meters
Coiled Hose Trick
An Uplifting Experience!
Pascal's Vases
Divers exhaust during ascent
Balloon in Bell Jar demo.
The Bends
Dams
Cut Steel with water jet
Press at center of Earth = 1 X106 atm Temp = 4000oC
Pascal's Vases
Burst the Barrel
Disintegrate the Jug
Hydraulics Demos:
Brakes
Lifts
Presses  (make diamonds)
Syringe pistons
King Hiero's Fountain
An uplifting experience (vacuum cleaner & garbage bag).
Pushy Balloons

Total Force = (pressure)(area)

TF = pA

The Spygmomanometer measures blood pressure
in millimeters of mercury.

A larger surface area on the outer edge of the tube gives a greater total force.
Hence the tendency to straighten out under pressure.

Hint: Pressure = (depth)(density)

Total force = (average pressure)(area)

Solution to the above problems:

Pascal's Law applied to the water rocket Video:

The pressure is transmitted undiminished
in all directions!

The fluid pressure from the master cylinder
is transferred equally to all the brake shoes.

Pascal's Hydraulic pistons can crush a car with a body in the trunk. Video:

An Uplifting Experience. Total force = pressure X area. Video:

Hydraulics easily lifts a house, Video:

Total Force = Pressure X Area. Movie

Notice the spaces between the blocks.

Bernoulli and his Equation

The Coanda Effect

The Coanda Effect is the tendency of a fluid jet to stay attached to an adjacent curved surface that is very
well shaped by a combination of the greater pressure above the fluid flow and the lower pressure
below the flow caused by an evacuating effect of the flow itself.

Demos: Spoon with water flowing over the convex surface, blow out a candle that is behind a beaker or finger.

Airplane Lift

A Bernoulli Ball and a TP attack! Video:

Bernoulli in the shower!

Attacked by a fierce, wild shower curtain.

Demos of pressure:

Forces & Pressures of a Brick.
Measuring Pressure Demos:
The open & closed tube manometer.
The Bourdon Gauge.
Pascal's Vases
Disintegrate the Jug
Hydraulics Demos:
Syringe pistons
King Hiero's Fountain
An uplifting experience, garbage bag & vacuum cleaner blower
Pushy Balloons. Small one gets smaller, large one gets larger
Disintegrate the 4-liter Jug
The BAM Can for pressure!

Demos of Bernoulli:

Spool & Paper Blow
Papers blown together
Airplane Lift
Curve Baseball
The Brass Aspirator
Carburetor
Ping Pong ball over vacuum cleaner blaster
Convertible Top Bulge
Shower Curtain Hugger with papers
Pop can attraction
The  battle between  Coke & Pepsi

Here Endeth Pascal & Bernoulli