Compressed Air Science Project
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Written by Dee
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Saturday, 07 July 2007 |
Air pressure and compressed air science experiments and science fair projects.
Compressed Air Science Project
The fact that we not only make use of air pressure but also of compressed air is familiar to us all. Automobiles weighing several thousands of pounds are held up by compressed air. The construction of bridge foundations and tunnels under the beds of rivers is made possible by it. Moving trains weighing hundreds of tons may be quickly brought to a stop by the air brake. Drills, riveting machines, and many other appliances are operated by compressed air. How such a substance as air can do all these things opens up for us many problems.
Science Fair Project Idea: How air pressure is used in building foundations and subways. What is an air bubble? Can air and water occupy the same space at the same time?
Science Experiment for Compressed Air and Air Pressure
To find out if air and water can occupy the same space at the same time, push down into a vessel of water an inverted drinking glass. What is the result? It is evident that the pressure of the air within the glass is sufficient to prevent the entrance of the water into the glass.
This pressure is equal to the weight of the column of water above the level of the water which is inside or the glass plus the ordinary atmospheric pressure (how much?) on the surface of the water. As the glass is pushed downward will any change occur in the amoun^ of pressure exerted by the contained air? At what depth in the water will the air exert a pressure equal to two atmospheres? At this point the volume of the air will be one half of its original volume, illustrating a law of every true gas, that the volume varies inversely as the pressure exerted upon it. This law is known as Boyle's law.
Caissons used in building foundations under water are large metal cylinders open at the bottom, into which air is pumped until it exerts sufficient pressure to prevent the entrance of water (Figure 21). Air under pressure was used to keep out the water during the construction of the tunnels under the East and North rivers at New York City.
Great care must be taken by men passing from the compressed air chambers to the outer air. If this is done too
quickly, gases which are dissolved in the blood form small bubbles which prevent the blood from passing through
capillaries (very small blood vessels), causing an acute disease, the " bends." To prevent this, a man instead of
passing directly into the outer air goes through several rooms of graduated pressures, remaining in each room a
sufficient length of time to permit the body to accommodate itself to the changed pressure. Questions to answer: If the pressure of the air in the caisson is about 30 pounds per square inch, how far from the surface of the water is the bottom of the excavation ? What would happen if the doors at the top should be left open ? Why ?
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Last Updated ( Sunday, 22 July 2007 )
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