Atmospheric Pressure
Properties of Matter

Cup Trick

Enrichment Activity for 5-11 11-14


What you need

  • Two identical paper or plastic cups

Instructions

  1. Take two empty cups and put one inside the other
  2. Hold them quite close to your mouth and blow between the rims of the cups

Results and Explanation

If you blow softly the inner cup rises up slowly. If you blow hard the top cup launches itself across the room.

Moving air has a lower pressure than still air, so, as you blow, you lower the air pressure between the rims. As the still air in the bottom of the cup is at a higher pressure, it forces the top cup up and out.

Atmospheric Pressure
is a special case of Pressure
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