Wednesday, September 12, 2012

Science Blows Me Away!

In this blog we achieve an effect that appears to defy gravity. In fact it uses the principle that a Swiss bloke called Daniel Bernoulli. He talks about it in his book Hydrodynamica in 1738.

To do this experiment you need:

  • Hair Dryer 
  • Ping Pong Ball

  1. Hold the hair dryer so its blowing straight up. Hopefully it will have a cold setting. 
  2. Hold the ball above the the dryer and let go. 
  3. With a bit of practice the ball should float in front of you.

This is thanks to what is called the 'Bernoulli Principle'.

There are two forces acting:
- The force of the moving air is pushing the ball up.
- The force of Gravity is pulling it down.

The point where the ball is floating is where the two forces are equal. One is not stronger than the other. As a result of the air moving means there is lower pressure in this part of the air compared to air around it. The air at the greater pressure helps to hold the ball in place. All this together makes the ball float.
Things you might want to try 
  • Can you move the hair dryer left and right without the ball dropping? 
  • What happens if you slowly tilt the hair dryer at a angle? 
  • Can you catch the ball in a cup as it floats?
We'll be demonstrating this experiment at our NZ-ED Show sessions over the next few days.  See you there!

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