Floating Ping Pong Balls
Gravity is a mysterious thing. We experience its effects every day but never really think about. Not enough gravity and we’d be floating around in space. Too much gravity and we’d be flattened like a pancake. Luckily, the gravitational pull is just right here on Earth. It keeps us comfortably anchored to the ground. Still, it helps to understand that with regards to gravity, there are opposing forces at work.
Another principle demonstrated in this experiment is the Bernoulli Principle. The Bernoulli Principle states that as an air stream (or fluid) speeds up, a decrease in pressure occurs. Fast moving air will cause a drop in air pressure (relative to the air pressure outside the column of moving air).
- Turn hair dryer on highest setting
- Point hairdryer upward so air is blowing straight up
- Gently place ping pong ball above the hair dryer
The ping pong ball will float about the hair dryer, spinning and bobbing gently, but will not fly out of the air stream. The moving column of air produced by the hair dryer causes an area of low pressure (due to the Bernoulli Principle as explained above). The pressure in the column of air is lower than the pressure outside of the column of air. The ball cannot move into the area of the higher pressure air. When it moves in that direction, the higher air pressure pushes it back into the low pressure column of air. Hence, it floats above the hair dryer and does not fly across the room.
Gravity comes into play when examining how high the ball goes before it gently bobs back down. The hair dryer pushes the ball upward until its upward force equals the force of gravity that is pushing down on it – that’s where it stays.