Air Pressure - Newspaper

Common Student Misconception: 

"There cannot be any pressure around us, since we cannot feel it."

In an airplane you can feel the pressure in your ears, particularly during take offs and landings.  When opening a soda can you can hear the change in pressure as the gas escapes.

Demonstrate the breaking of a ruler covered with one sheet of newspaper by placing a cheap yardstick on a table with about half of it extending past the edge.  Carefully spread a full page of newspaper over the portion of the yardstick on the table.  (Press paper against the yardstick to expel air, smoothing the paper flat against the tabletop.)  Then, with a karate-like blow, chop off the portion of the yardstick that extends beyond the table.  Students can calculate the amount of pressure on the newspaper.

       Air pressure is 14.7 psi.       

The pressure on top of the newspaper is about 4 tons.