Here is a great way to show middle school students Bernoulli's Principle in action. I personally used this while teaching eighth grade.
Bernoulli's Principle states that an increase in velocity of moving fluids is accompanied by a decrease in the fluid's pressure. Yeah that sounds hard to understand. Once going through the hands on activities in class students really do understand the concept.
We have six hairdryers placed around the classroom (we would have more but we blow a fuse). The students work in groups of four starting out with predicting what will happen if they drop a ping pong ball down on a hairdryer that is on lowest setting. We then predict what would happen if we had the dryer on the highest setting.
Now we predict what will happen if we gently "set" the ball into air flow coming out of the dryer. Which setting is best to keep the ball from getting shot across the room? We then gently "set" the ball into the flow of air coming out of the hair dryer.
There is a lot of predicting, inferring, and observing throughout this activity. Great for the science teacher to get their students thinking and inspired to learn more.
Step 1: Materials
For this activity you will need a hairdryer, ping pong ball, and for added fun an empty paper towel roll or toilet paper roll.
Hair dryers with very high speed velocity works best. Also we would recommend a hairdryer that has a cool setting.
Step 2: Just Right
Place the hairdryer onto highest speed and coolest air setting.
Gently lower the ping pong ball on to the flow of air coming out of the dryer and let go. This may take a bit of practice to get it just right.
Do not give up. You will get it.
Step 3: Float
Once set right into the stream of air the ball will float above the hairdryer. The air around the ball is creating an area of low pressure. The fast moving air is low air pressure. The air in the room becomes high air pressure, relatively speaking. This high pressure air pushes on the ball equally in all directions, keeping the ball in place.
Step 4: Now the Magic
Now that the ball is in the stream of air, slowly turn the hairdryer toward it's side. Magic!
The really cool think is when the ball stays floating when the hairdryer is not under the ball. It looks like magic but it's science! As before, the fast moving air creates an area of low pressure. The slow air in the room becomes high pressure and pushes on the ball in all directions, keeping the ball suspended in air.
Step 5: Video and More
Here is a minute video of Bernoulli's Principle in action. Wait to the end to see the reason for the roll. It is a nice little surprise when doing the activity.
Here is a link to a previous Instructable we did with Bernoulli's Principle that is a great demo. Flying Toliet Paper
This is an entry in the
Classroom Science Contest