Ruler Snap

The Weight of Air Breaks the Ruler.

 

 

 

Category - Solids, Liquids & Gases

Key Idea - Air Pressure

 

Purpose - Demonstrates the fact that air has mass and must be moved through. 
Nature -  Demonstration
Materials -  30 cm wooden ruler, large sheet of newspaper
Method - 
  1. Place the ruler on the edge of a bench or table with half hanging off the edge.
  2. Place the newspaper flat on top of the bench, covering the half of the ruler on the bench.
  3. Very quickly and solidly give the end of the ruler hanging over the edge a smack downwards.  The ruler should break at about the edge of the bench, and the newspaper should not a have moved.
Safety - Nil
Explanation - To move the newspaper, a considerable amount of air must be pushed aside.  Because of the speed of the blow in this case, the slowness of the newspaper movement acts as an anchor and causes the ruler to break.
Notes - The faster the blow, the more likely this will work.  If you are keen to avoid the pain of the blow you can use another ruler edge on as the striking implement.