So you think you know how much atmospheric pressure is, huh? This long aluminum bar is one inch square and weighs about 15 pounds. Mess with this thing and you begin to appreciate just how big atmospheric pressure is! This aluminum bar is 1-inch square in cross section, about 4 m long, and weighs about 14 lbs. Therefore, if it is held vertically, the end of the rod exerts a gauge pressure of 14 psi. It can be carefully placed on the toes of a volunteer wearing closed-toe shoes and they can relate their sensations to the class.
This demo is most commonly performed at the beginning of the unit on ideal gas laws, but it could also be useful when derived units are first introduced at the beginning of the year. Allow about 5 minutes for this demo.