In celebration of Earth Science Week (Oct 10th to Oct 16th), why not try and make a tornado in your kitchen? With your parents’ permission first, of course!
Stuff You Need:
- Two plastic 2-litre fizzy drink bottles
- Plastic washer
- Masking tape
- Food colouring
- Water
What To Do:
- Remove the caps from the two empty bottles.
- Fill one soft drink bottle half-full with water and add a couple of drops of food colouring.
- Place the plastic washer over the opening of the bottle.
- Turn the other bottle over and place it on top of the first bottle, neck to neck, with the washer wedged between.
- Wrap masking tape around the two bottles' necks to tightly attach the bottles to one another. You might need a lot of tape.
- Turn the bottles over so that the full bottle is on top. Lightly shake the bottles in a circle so the water begins to swirl.
- Place the bottles on a table. Watch the water drain from the top bottle to the bottom.
You Will Notice:
You’ve just created a tornado in a bottle! A tornado is a type of vortex, which is a spinning column of air with some water vapour. Tornadoes are formed below strong thunderstorms when warm, humid air tries to push through cool, dry air. Pushed by a cross wind, the air begins to swirl forming a funnel cloud.
In the experiment when you spin the bottles around a few times, the water in the top bottle starts rotating. As the water drains into the lower bottle, a vortex forms. The water is pulled down and forced toward the bottle opening in the centre by gravity. To make water move in a circle, forces called centripetal forces must act on the water. These forces are provided by a combination of air pressure, water pressure, and gravity.
You can tell where the centripetal forces are greater by looking at the slope of the water. Where the water is steeper, such as at the bottom of the vortex, the centripetal force on the water is greater. Water moving with higher speeds and in smaller radius curves requires larger forces. The water at the bottom of the vortex is doing just this, and so the wall of the vortex is steepest at the bottom.
When you’ve completed the experiment, you can visit the Earth Science Week website by clicking here:
http://www.earthsciweek.org/