Bernoulli’s Principle
Objectives:
1. state Bernoulli's Principle
2. list two places where the Bernoulli Principle
can be found in action
3. explain two examples of the Bernoulli
Principle
Bernoulli’s Principle
the pressure of a fluid
decreases as the
speed of the fluid
increases
First Examples
1. paper goes up when you
blow over it
• fast air over the top
• still air on the bottom
• lower pressure on the top
2. narrow river flow faster than
wide rivers
• same volume of water must
pass through the gap
• more water goes through
less area
Stormy Examples
3. tornadoes and hurricanes blow the roofs off
houses and blow out windows
• fast moving air outside has very low pressure
• the faster the air, the lower the pressure
• air inside has higher relative pressure
• everything blows out
• prevent it by opening up the windows
Home Examples
4. the shower curtain
blows in when you
run the water
• water moving inside
causes air to move
• higher pressure
outside pushes
curtain inward
The Classic
Example
5. flight
• curved part of wing on top
• air going over the top moves faster than air
going under the wing
• faster air has lower pressure so high
pressure underneath pushes wing up
The Cute Example
6. Prairie Dog Holes
• live in burrows underground
• one end has a mound to raise its
elevation
• pressure depends on depth
• air moves faster slightly off the
ground
• low pressure at top of mound
sucks air through the tunnel
• same principle for ant colonies
Woodchuck Burrow
The High Tech Examples
7. passing high speed trains
• tracks for high speed trains need to be further apart
• high speed of passing trains causes low pressure
between them
• higher pressure on outside pushes trains towards
each other
The Reverse Classic Example
8. spoilers on cars
• curved part of spoiler on bottom
• slower moving air over the spoiler pushes
car down onto the road
• result is better traction and ability for
higher speed with control