| The Atmosphere Learning Lessons |
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Learning Lesson: Go with the Flow |
| OBJECTIVE |
The students will discover that the faster air moves, the lower the pressure becomes within that flow of air. |
| OVERVIEW |
Create low pressure by blowing between two soda cans. |
| TOTAL TIME |
5 minutes |
| SUPPLIES |
Two (2) empty soda cans
Level surface |
| PRINTED/AV MATERIAL |
None |
| TEACHER PREPARATION |
None |
| SAFETY FOCUS |
Severe thunderstorm safety rules |
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| Background |
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None.
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| Procedure |
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- Lay the two cans parallel to each other, about one inch apart, near the edge of a level surface.
- Put your face down near the surface and blow between the two cans.
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| Discussion |
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The two cans will roll together. In fact, the harder they blow, the faster the cans move toward each other. This is the Bernoulli's Principle in action. Bernoulli discovered that the faster a fluid flowed, the lower the pressure that was within that fluid.
By blowing between the two cans, you are making the air between them move faster than the surrounding air (which is basically calm). The cans roll together as the higher pressure surrounding the two cans (away from the air flow) pushes the cans together.
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| Live Weatherwise |
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Severe Thunderstorm Safety
Spring is the season most of the severe thunderstorms occur. This is due partly to the jet stream that moves over the country. The faster the jet stream is, the lower the pressure becomes in that stream. This lower pressure acts like a vacuum and draws air up, therefore allowing the thunderstorms to form and quickly become severe. When thunderstorms approach...
- REMEMBER that if you can hear thunder, you are close enough to a storm to be struck by lightning. Go to safe shelter immediately!
- Move to a sturdy building or car. Do not take shelter in small sheds, under isolated trees, or in convertible automobiles.
- If no shelter is nearby or available, get in the hard top car and keep the windows up.
- If you are boating or swimming, get out of boats and away from the water, get to land and find shelter immediately.
- If you are indoors, unplug unnecessary appliances and use the phone only for emergencies.
- If you are caught outside and no shelter is available:
- Find a low spot away from trees, fences, and poles
- Squat low to the ground on the balls of your feet, place your hands on your knees with your head between them, make yourself the smallest target possible and minimize your contact with the ground.
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| Fast Facts |
| The average size of the diurnal pressure change at the equator is 1.16 millibars. This daily change decreases to about 0.17 millibars at 45° N/S latitude. |
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