Aspirator Demonstration

A common device which makes use of the Bernoulli principle is the aspirator. When water is forced through a smooth constriction, the fluid velocity increases, lowering the pressure below atmospheric pressure. This can entrain air into the tube at the constricton and be used to partially evacuate the air from an attached volume. But I'll bet you didn't think such a device could remove enough air so that the atmospheric pressure would crush a 55 gallon drum! But Dan Stamm, physics teacher at Campbell High School near Atlanta demonstrated just such an aspirator marvel in his physics classroom.

The aspirator was used on the laboratory sink in Dan's laboratory room, and he had a pressure sensor attached to the drum. He lowered the pressure in the drum to about 40 kiloPascals, about 40% of atmospheric pressure. The drum used had a surface area of about 3000 square inches, so a 40 kPa internal pressure would cause the atmosphere to exert a net inward force of about 26,000 pounds or 13 tons on the walls of the drum.