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2 - Fluid Mechanics

Surface Tension

Statics Of Fluids

Dynamics Of Fluids

2A - Surface Tension

2A10 - Force of Surface Tension

Force of surface Tension (2A10.10)
A square wire frame with the bottom side free to slide is dipped in soap solution and pulled out; the surface tension of the soap film pulls on the sliding wire.

Floating Metals (2A10.20)
A sewing needle, paperclip, or a piece of Aluminum foil floating on water.

Surface Tension Disc (2A10.33)
Lift a floating disc off a water surface with a spring or spring scale to show the force needed to overcome surface tension.

Pepper and Soap (2A10.40)
Black pepper is sprinkled on a dish of water. Add a drop of soap in the middle.

Soap Bubbles (2A10.50)
Blow soap bubbles.

2A15 - Minimal Surface

Ring and Thread in Soap Film (2A15.10)
A loop of thread is tied across a rigid square frame, which is dipped in a soap solution. The thread will float limply in the soap film until the film inside the loop is punctured; the loop will then spring into a circle due to the surface tension of the soap film outside it, forming a surface of minimum energy.

Soap Film Minimal Surfaces (2A15.20)
Wire frames of various sizes and shapes are dipped into a soap solution, and form surfaces of minimum energy.

2A20 - Capillary Action

Capillary Tubes (2A20.10)
Glass capillary tubes with different size bores all sit in a reservoir of colored water - the water rises to different heights in each tube.

Capillary Action (2A20.35)
A small glass capillary tube is lowered into a resevoir of colored water which jumps up the tube.

2B - Statics Of Fluids

2B20 - Static Pressure

Pressure vs. Depth (2B20.15)
Status: Unavailable
An electronic pressure gauge is lowered into a tall column of water. As the sensor is lowered, the increasing pressure is displayed on a LED bar graph.

Pressure vs. Depth in Water and Alcohol (2B20.16)
Status: Unavailable
The electronic pressure sensor and LED bar graph display are used first in water and then in alcohol.

Hydrostatic Paradox (2B20.34)
A truncated glass cone is open at both ends and fits against a flat glass plate. If the plate is held against the wide side of the cone and submerged in water, it will hold tight due to the pressure differential between the air inside and the water outside. With the plate against the small end of the cone, however, it will not stay put due to the smaller area of pressure differential.

Pascal's Vases (2B20.42)
Tubes of various shapes rise from a common horizontal tube. When filled with water, the level is the same in each tube.

Hydraulic Press (2B20.60)
A hydraulic press with a large pressure gauge easily breaks boards.

2B30 - Atmospheric Pressure

1 Atmosphere 'bar' (2B30.05)
A 1" square bar of steel is cut to weigh 14.7 pounds. When stood on its end, it exerts a pressure of 14.7 psi, or 1 atm.

Crush a 55 Gallon Drum (2B30.20)
Boil water in a 55 gallon drum, seal, and then cool. This is by far, one of the most impressive demos that we have. Note: Our barrel supply is VERY limited so talk to us if you're interested in this demo.

Crush a Can with a Vacuum Pump (2B30.25)
Evacuate a one gallon metal can and it will collapse from the air pressure on the outside.

Magdeburg Hemispheres (2B30.30)
Two small hemispheres with handles are pressed together and evacuated; they cannot be separated by hand due to the unbalanced pressure on the outside.

Suction Cup (2B30.36)
A large, 4" diameter, suction cup of the type used to carry large panes of glass has a small hole in the top. If the suction cup is squeezed down onto a table and the hole covered with a finger, a student will not be able to pull the suction cup off the table as long as your finger covers the hole.

Card on Inverted Glass (2B30.45)
Fill a glass with water, place a stiff card over opening and invert. Card remains in place due to atmospheric pressure below card.

Stool and Rubber Sheet (2B30.50)
A square rubber sheet with an attached handle is set on top of a wooden stool or other heavy object. The weight of the sheet drives the air out from beneath it, and the air pressure on the outside holds the sheet and stool together. The stool can now be lifted by pulling up on the handle.

Adhesion Plates (2B30.55)
Status: Unavailable
Two very flat glass plates will stick together without adhesives due to the unbalanced pressure on their outside surfaces.

Vacuum Cannon (2B30.70)
A long PVC pipe contains a ping pong ball at one end. Both ends are sealed and the tube is then evacuated by a vacuum pump. When the seal is broken at the end with the ping pong ball, atmospheric pressure accelerates the ball and gives it enough kinetic energy to destroy empty aluminum cans.

2B35 - Measuring Pressure

Mercury Barometer (2B35.10)
A simple mercury barometer.

Mercury Barometer in Vacuum (2B35.15)
A mercury barometer is enclosed in a tall bell jar. The tube is evacuated, and the height of the mercury column falls to zero.

Aneroid Barometer (2B35.40)
Has a glass back to show the mechanism.

2B40 - Density and Buoyancy

Buoyant Force (2B40.14)
Two large scales show the weights of a container of water and of an aluminum cylinder. When the cylinder is lowered into the water, its weight as shown on the scale decreases; the weight reading of the water container simultaneously increases by the same amount.

Floating Board and Weights (2B40.18)
A board sinks equal amounts as equal weights are added.

Archimedes' Principle and Crown (2B40.20)
A spring scale supports a plastic bottle and an aluminum cylinder on a string. The aluminum cylinder is lowered into a water bath and the displaced water that spills out is collected in a large beaker. The weight reduction of the cylinder is noted on the scale. Then the water that was displaced is poured into the plastic bottle tied to the scale and the scale reading returns to its original value, showing that the buoyant force is equal to the weight of water displaced. Can be repeated with an irregularly shaped object (a gold crown) to find that it is, unfortunately, a fake.

Float a Battleship in a Bathtub (2B40.25)
A large block of wood will float in a container that is only slightly larger with a small amount of water.

Cartesian Diver (2B40.30)
A Cartesian diver is controlled by squeezing a bulb attached to the water column. Increased pressure decreases the air volume in the diver and lowers its buoyancy so it sinks. Release the pressure and the diver returns to the top.

Helium Balloon in Helium (2B40.43)
A helium balloon is placed in a large glass bell jar, and it floats to the top. Helium is then leaked into the jar with a hose, and when the air has all been displaced the balloon sinks to the bottom. Pick the jar up and the balloon floats on the helium/air interface. Note: Helium is becoming scarce so this demo may not always be available.

Weight of Air (2B40.45)
An evacuated 1 liter flask is placed on a digital scale. Air is then readmitted to the flask, and the extra weight of the air increases the reading on the scale.

Water and Mercury in U-Tube (2B40.53)
Measure heights of liquid boundaries and use the data to calculate relative densities.

Density Ball (2B40.59)
A metal sphere barely floats in cold water and sinks in hot water.

Hydrometer (2B40.60)
Hydrometers float in two different liquids to demonstrate liquid density measurement and buoyancy.

Different Density Woods (2B40.61)
Three similarly sized blocks of wood float at different depths, or simply sink in water. Unfortunately the type of wood is unknown.

Density Balls in Beans (2B40.85)
A ping pong ball will rise and a steel ball will sink in a shaken beaker of beans.

2B60 - Siphons, Fountains, Pumps

Hero’s Fountain (2B60.10)
A clever arrangement of reservoirs connected by tubes that forces a stream of water above the highest reservoir.

Siphon (2B60.20)
Siphon water from one beaker to another.

2C - Dynamics Of Fluids

2C10 - Flow Rate

Torricelli's Tank (2C10.10)
A tall tank of water has three holes at different heights. Water streams out these holes with different velocities depending on their depth.

Syringe and Water (2C10.26)
A large syringe is used to show the change in velocity with changes in tube diameter. Fill syringe with water, then point into the air and press the plunger. Your thumb, and the water in the wide part of the syringe, are moving slowly, but the water emerging from the narrow tip has a high velocity.

2C20 - Forces in Moving Fluids

Venturi Tubes (2C20.10)
A horizontal pipe with a constriction in the center has four pressure manometers attached along its length. Air flows at high speed through the pipe. Pressure decreases uniformly along the pipe, as shown by three of the manometers, but the manometer attached at the constriction shows a lower pressure than expected due to the increased air velocity (Bernoulli's Principle).

Pitot Tube (2C20.25)
A pitot tube is connected to a water manometer and the air stream velocity is varied.

Ball in an Air Jet (2C20.30)
A high velocity air stream supports large styrofoam balls and holds them in place due to the greater pressure outside the air jet.

Ball in a Funnel (2C20.35)
Air blowing out of an upside down funnel will hold up a ping-pong ball.

Suspended Plate in Air Jet (2C20.40)
A horizontal metal plate has a hole in the center out of which air flows downward at high velocity. A second plate pushed up against the first will cling to it due to the high velocity (low pressure) of the air flowing between them.

Card and Spool (2C20.41)
A card with a small pin stuck through into the spool will be suspended when you blow into the spool.

Suspended Parallel Cards (2C20.45)
Air passing between two hanging cards pulls them together.

Airplane Wing (2C20.50)
A curved sheet of aluminum is lifted upwards when a high speed air jet flows over the surface.

Flettner Rotor (Magnus Effect) (2C20.80)
A cart has a motorized styrofoam cylinder mounted vertically. When the cylinder rotates at high speed, air from an air track blower passing around the cylinder will make the cart move at right angles to the air stream.

2C30 - Viscosity

Bubbles in Oil (2C30.25)
Three tubes containing different oils with different viscosities each have an air bubble at the top of the tube. Turn over the rack holding the tubes, and the bubbles will drift up at three different terminal velocities.

Viscous Drag in water (Terminal Velocity) (2C30.50)
Small balls slightly denser than water are dropped into a tall cylinder of water. Viscous drag slows the balls as they sink, giving them a low terminal velocity.

Air Friction (2C30.65)
Drop two pieces of paper simultaneously, with one flat and the other crumpled into a ball.

2C40 - Turbulent and Streamline Flow

Turbulence Sphere
A glass sphere filled with rheoscopic fluid can be spun to produce visible turbulent (and some not-so-turbulent) flow of the fluid.

2C50 - Vorticies

Tornado Tube (2C50.30)
Two plastic bottles are joined together at the necks by a small orifice and partially filled with water. Turn the pair over and give it a swirl and a tornado will form, with air coming up through the center and water going down the periphery of the orifice.