1. Bernoulli’s Principle
For a fluid traveling // to a surface:
…FAST-moving fluids exert LOW pressure
…SLOW- “ “ “ HIGH “
LIQUID
OR GAS
roof in hurricane
FAST
LOW P
SLOW
HIGH P
SLOW
FAST
LOW P
HIGH P

2. airplane wing / helicopter propeller
Resulting Forces
(BERNOULLI’S
PRINCIPLE)
(GRAVITY)
AIR
PARTICLES
FAST
LOW P
SLOW
HIGH P
frisbee

3. Bernoulli’s Principle
Faster moving air on top  less air pressure
Low Pressure
Air foil
What is an airfoil?
An airplane wing has a special shape called an airfoil.
As a wing moves through air, the air is split and passes above and below the wing. The wing’s upper surface is shaped so the air rushing over the top speeds up and stretches out. This decreases the air pressure above the wing. The air flowing below the wing moves in a straighter line, so its speed and air pressure remain the same.
Since high air pressure always moves toward low air pressure, the air below the wing pushes upward toward the air above the wing. The wing is in the middle, and the whole wing is “lifted.” The faster an airplane moves, the more lift there is. And when the force of lift is greater than the force of gravity, the airplane is able to fly.
High Pressure
LIFT
Slower moving air on bottom  high air pressure
Air moves from HIGH pressure to LOW pressure

4. Bernoulli’s Principle
Fast moving fluid exerts low pressure. Slow moving fluid exerts high pressure.
Fluids move from concentrations of high to low concentration.
LIFT
AIR FOIL (WING)
Pressure exerted by slower moving air

5. "Creeping" Shower Curtain
COLD
SLOW
HIGH Pressure
WARM
FAST
LOW Pressure

6. WINDOWS BURST OUTWARDS
FAST
LOW P
SLOW
HIGH P
TALL BUILDING
A TORNADO WATCH simply means that conditions are favorable for tornadoes to develop. In this case you should take precautions to protect you and your property, and listen to the radio to keep informed. Tornadoes are most likely to occur in the late afternoon on a hot spring day. However, tornadoes have occurred in every month at all times of the day or night. When a tornado "watch" is issued, be alert for changes in the weather. Be prepared to act quickly.
A TORNADO WARNING means that a tornado has actually been sighted. If one is issued for your area, you should seek shelter immediately! There is little time for closing windows or hunting for a flashlight. It's a good idea to know where things are, and to have an emergency storm kit already prepared.
WINDOWS BURST OUTWARDS
windows and high winds (e.g., tornadoes)