- Bottle (big is better) with lid
- Aluminum foil
- Battery, C
- Film can, no lids necessary
- Resistance wire
- Small paper clips
- Big bottles for impeller
- Glue stick piece for impellor
- Drill platform
- 19/64 bit for drill (sharp)
- 2 rasps or course sand paper to rough - - up the cap
- Wire strippers
- Coloring for water
- Black tape
A battery powers this tornado. Real tornados – and all weather patterns – are powered by the sun. Radiation from the sun warms the earth differently according to many factors such as reflectivity of the surface and cloud cover. Hot areas and cold areas then lead to different air pressures. Wind is basically air moving from high to low pressure, and the greater the difference, the stronger the wind. Hurricanes and tornadoes are special situations where a local area of very low pressure (a large area for a hurricane and a small one for a tornado) becomes the center of strong rotating winds.
Why do the winds blow around in circles? Rotation is a common, stable situation in nature. For example, all known planets and their satellites are rotating. For another example, try to shake a bottle of water soda from side to side, and then hold it still. Invariably, the liquid is rotating when you finish. In technical terms, the winds of hurricanes and tornados are merely conserving their momentum, as all things must.
More batteries make the motor spin faster, and weaker batteries make is spin slower. Changing the size of the impellor is more complex. A very large impellor turns slowly because it has to push a lot of water, and the motor is not strong at slow speeds. A very small impellor turns fast but can only push a tiny bit of water so it can’t get the whole bottle of water moving fast. The optimal size is somewhere in between. The shape is also important. A boat’s propeller is much smaller and shaped differently than an airplane’s. The best size and shape depend on what kind of fluid is being pushed and at what speed the motor is most efficient.
Changing the wires on the battery will make the motor and tornado turn in the opposite direction. In this project, and in most human-made vortices, your hemisphere is not important; the vortex turns in the direction that you drive it. But your hemisphere is important when considering hurricanes and all large pressure systems. Large low-pressure systems in the northern hemisphere turn counterclockwise, because they occur on the surface of a spinning sphere – the earth. The force that makes this happen is called the Coriolis force.
Tornadoes are much smaller and localized than hurricanes. Most often they are formed from the midst of a single thunderstorm and last only minutes. Most rotate counterclockwise, but some have been seen to go the other way.
If you put some glitter or bits of paper in the bottle and follow them, you’ll see that they are going around and around, but also up and down. The up and down motion is also circular. They go down near the center of the bottle, and back up near the outside.
Fluids are liquids or gases (vapors).
Tornados, hurricanes and whirlpools all have this sort of motion. In those cases, the rotation is caused by pressure differences (they are not in a bottle).
Impellors throw fluids outward. Propellers throw fluids forward or backward.
How could you make the tornado spin faster?
How can you make it spin slower?
What would happen if you put the spinner and lid on a big bottle?
What is the path of a little piece of water in the bottle as the tornado is spinning?