Air is a mixture of gases: oxygen (about 21%), nitrogen (78%),
and the inert gases argon, neon, helium, krypton and xenon (1%).
Moreover, air contains small amounts of hydrogen, methane,
carbon dioxide and water vapour. Has air got weight ?
Yes: a cubic foot of air weighs about 1.33 oz. A room 15 ft
square and 9 ft high contains about 170 lb of air. The weight of all the air on the earth is 11,000,000,000,000,000,000 lb.
What is air pressure ? The force that the air exerts upon
everything. By pressure we mean the force with which the air presses against one square inch of a wall. The unit of pressure is the atmosphere that
is a pressure of about 14.5 lb per square inch, which means a force of 14.5 Ib on every square inch. At sea-level the average pressure is one atmosphere.
Our project today tested Bernoulli's Principle. This principle states that for a fluid
undergoing steady flow, the pressure is lower where the fluid is flowing faster. In this
lesson, the "fluid" with which we are concerned is air. Fluids
include liquids and gases and air is a mixture of gases and therefore a f
The antique toy is a great demonstration of Bernoulli's Principle. Blowing through the wooden pipe, floats the ball steadily over the pipe. Experiment at home with other balls and paper shapes. You can experiment with a hairdryer too.