Can you make a table tennis ball remain in the air by blowing at it ?
Let’s find out.
What you need: a straw which is approximately 15cm long and a table tennis ball.
What you do:
- Put one end of the straw in your mouth.
- Tilt your head back and hold the table tennis ball 6-8cm above the other end of the straw.
- Now blow as hard and as quickly as you can, and let go of the ball.
What you find:
The ball does not fall down, it stays in the air and the harder you blow, the higher it will go above the straw.
Why doesn’t it fall down?
When air moves quickly, its pressure reduces- this is the Bernoulli Theorem. The air that you blow out quickly comes out of the straw and moves around the ball and forms a region of lower pressure over the ball.
When you blow hard, the ball stays in the air or goes higher above the straw. It cannot move in any other direction because the greater air pressure on the sides of the column of air which you are blowing makes the ball stay in the column.
The Bernoulli Theorem also explains why a kite goes up in a strong wind and a heavy aircraft floats while frying.