2A - Surface Tension
20. Capillary Action
2A20.1 Capillary Tubes
A (small) set of capillary tubes of various radii.
[Set-Up Time: 5 min.]
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2B - Statics of Fluids
20. Static Pressure
2B20.1 Pressure vs. Depth
A large cylinder with holes at different heights is filled with water. The higher pressure at greater depth forces the water out with greater horizontal velocity.
[Set-Up Time: 10 min.]
2B20.2 Cylinder with Dropping Plate
A hollow cylinder is lowered into a larger vessel filled with water. The bottom of the cylinder is a loose plate which is held tight by the external water pressure. The cylinder is gradually filled with colored water, and when the height of the water is the same in both containers, the plate falls away.
[Set-Up Time: 10 min.]
2B20.3 Pascal's Vases
Tubes of various shapes are joined at the bottom. Filled with water, the level will reach the same height in all tubes.
[Set-Up Time: 5 min.]
30. Atmospheric Pressure
2B30.1 Vacuum Lift
A fifty pound weight is lifted when a cylinder with a piston is evacuated.
[Set-Up Time: 20 min.]
2B30.15 Crush a Can with Atmospheric Pressure
Boil water in a can, then invert over a pot of cold water and watch the can collapse.
[Set-Up Time: 10 min.]
2B30.30 Magdeburg Hemispheres
Two brass hemispheres are placed together and the inside is evacuated with a pump. Atmospheric pressure makes it very hard to separate them until the vacuum is released.
[Set-Up Time: 5 min.]
2B30.70 Vacuum Bazooka
A ping pong ball is sealed in a long evacuated pipe. When the seal on one end is broken, atmosphere propels the ball through the other end and through a soda can. This demo can be also set up with a motion sensor to calculate final muzzle velocity.
[Set-Up Time: 10 min.; with motion sensor 20 min.]
40. Density and Buoyancy
2B40.1 Archimedes' Experiment (Buoyancy)
A solid cylinder fits snugly inside a larger pail, and the two are balanced by an equal mass on the other side of a scale. The cylinder is then suspended below the pail and lowered into water, making the scale tip toward the other mass. Balance is restored by pouring the water displaced by the cylinder into the pail.
[Set-Up Time: 20 min.]
2B40.2 Cartesian Diver
A small diver (a cylinder closed on the top and filled with water and air) floats at the top of a large water-filled tube. Pressing on the rubber top of the tube increases the pressure throughout, forcing more water into the diver, changing its buoyant force and causing it to sink.
[Set-Up Time: 5 min]
2B40.3 Alternate Cartesian Diver
A diver floats in a soda bottle completely filled with water. Since the water is incompressible, squeezing on the bottle causes very little volume change but drives the diver straight to the bottom.
[Set-Up Time: 5 min.]
2B40.4 Weight of Air
An evacuated flask is balanced on a scale, and then air is allowed back into it.
[Set-Up Time: 20 min.]
60. Siphons, Fountains, and Pumps
2B60.1 Archimedes' Screw
A long, helical pipe is tilted 45 degrees and the lower end is inserted in water. Rotating the pipe moves water up to and out the top.
[Set-Up Time: 5 min.]
2B60.2 Intermittent Siphon
An inverted U-shaped tube inside a beaker will not siphon until the beaker is full; it then continues siphoning until the beaker is empty.
[Set-Up Time: 10 min.]
2B60.3 Hydraulic Lift Pump and Force Pump
Two types of pumps showing different methods of pumping water.
[Set-Up Time: 15 min.]
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2C - Dynamics of Fluids
10. Flow Rate
2C10.1 Uniform Pressure Drop
Water flows through a horizontal pipe, and three vertical tubes attached along its length demonstrate the decrease in water pressure.
[Set-Up Time: 10 min.]
20. Bernoulli Force
2C20.1 Bernoulli Tubes
Colored water is pumped through a horizontal tube which is narrower at the middle. Three vertical columns are attached to the tube, and the water rises to a lower height in the column over the constricted region of the tube. (Note that the offset pressure is much greater than the variation in pressure due to different velocities, so the effect is best seen by holding a meter stick horizontally across the three columns.)
[Set-Up Time: 25 min.]
2C20.2 Floating Ball
A Ping-Pong ball or tennis ball is held aloft by a jet of air. The hose can be tilted to a considerable angle before the ball falls.
[Set-Up Time: 5 min.]
2C20.3 Ball and Funnel; Spool and Card
A stream of air flowing out of a funnel holds a Ping-Pong ball in the funnel rather than blowing it away. Or, an index card will "stick" to a spool when air is blown through it.
[Set-Up Time: 5 min.]
2C20.4 Attracting Ping-Pong Balls
Two Ping-Pong balls suspended by thread will pull together when a jet of air is blown between them. Alternately, two sheets of paper can be used.
[Set-Up Time: 10 min.]
30. Viscosity
2C30.1 Viscosity of Various Liquids
A small panel of columns filled with various fluids can be inverted, showing the different rates at which air bubbles rise in each.
[Set-Up Time: 5 min.]
2C30.2 Terminal Velocity in Water and Karo Syrup
Two balls of different densities are dropped, first in water, then in Karo syrup.
[Set-Up Time: 10 min.]
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