Water-Glass Experiment

Air Pressure Experiment
This is one of the best examples of air pressure experiments with water.

• Take a glass and fill one-third of it with water. 
• Place a cardboard over the mouth of the glass. 
• The cardboard should be bit bigger than the mouth. 
•  Now put some pressure on the cardboard from the left hand and invert the glass with the right hand. 
•  Slowly remove the hand and see what happens. 
•  The water does fall from the glass, retaining the cardboard and the water in the same place as before.  
• This takes place because the air pressure outside,  ie.  14.7 psi,  is more heavier than the combining weight of the water and air inside the glass.