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Geologist
The Coriolis Effect is a subtle but very important part of meteorology. People still argue whether or not it affects bathtubs. Even meteorologists sometimes have difficulty explaining it carefully. Do not be discouraged if this section seems hard.
1.

 

 What is the Coriolis Effect?
www.weather.com/glossary/c.html

 
2. Lab: Effect of Rotation on Streams of Water (Coriolis Effect)

Referenced by:  Steve Carson, 609-452-6596, sc@gfdl.gov

“The Circulation of the Abyss” by Henry Stommel in Scientific American,  July, 1958, also in Oceanography, Readings from Scientific American, 1971, W.H. Freeman, pp. 71-76.

Materials:

                Turntables (lazy Susans) covered with dark paper

                Large cylindrical containers

                Thin dark tape to mark a diameter of the cylindrical containers

1 liter plastic bottles with the top portion cut off and a small hole a few cm from the bottom

Procedures:
Step1. 
Place the large cylindrical container on a turntable and place one of the 1 liter bottles in the center. Fill the bottle with water and line up the exiting stream of water with the diameter line. Viewed from above the water exits in a straight line. Rotate the turntable both counterclockwise (like the Northern Hemisphere) and clockwise (like the Southern Hemisphere) and observe how the stream is deflected to the right and to the left respectively relative to the direction it is moving.  
Step 2
Place the large container on the turntable and place two bottles against the wall of the container on opposite sides of the diameter line. Fill both with water and orient the streams to line up with the diameter line when observed from above and to meet each other near the center. Rotate the turntable both counterclockwise (CCW) and clockwise (CW). The streams should now diverge. They should both curve to the right (CCW) or left (CW) when looking in the direction of the flow.
Step 3
Place the large cylindrical container on a turntable and place two bottles against the wall of the container on opposite sides of the diameter line. Fill both with water and orient the streams to more or less parallel the side but in opposite directions relative to the direction of rotation. The streams should look straight when observed from above. Rotate the turntable both counterclockwise (CCW) and clockwise (CW). The stream that is flowing in the same direction as the direction of rotation should curve toward the wall of the large container. The stream that is flowing in the opposite direction as the direction of rotation should curve away from the wall of the cylindrical container. In both cases the curvature is to the right for CCW rotation and to the left for CW rotation when looking in the direction of the flow.

Explanation:

       Even though each little bit of water travels in a straight line relative to the non-rotating surroundings after it has left the hold, the bottle moves and changes orientation as the water is moving. The parts of the stream farther from the bottle have traveled longer and farther from the point that they exited the bottle than the parts of the stream closer to the bottle. The bottle has also moved more relative to the exit point of the farther parts of the stream than relative to the closer parts of the stream. This caused the stream to be curved. When the turntable is rotating counterclockwise the curvature is always to the right relative to the direction of the stream. This is analogous to the Northern Hemisphere of the Earth. When observed from above the North Pole the Earth’s rotation is counterclockwise. Flows in the Northern Hemisphere are diverted to the right due to the Coriolis effect. The opposite is true in the Southern Hemisphere: the rotation is clockwise when observed from above the South Pole and flows are diverted to the left.

        It is important to remember that these demonstrations on rotating disks are not perfect analogies to the Coriolis effect on Earth. Since the Earth is spherical the Coriolis effect varies from zero at the equator to a maximum at the poles. Also these demonstrations include another effect called the centrifugal effect so they do not show the pure Coriolis effect.  

 

Questions to Effect of Rotation on Streams of Water Lab

  1. What happened to the direction of the stream of water when you added water to the liter bottle in step 1? (This is before you rotate the turntable.)
  2. What happened to the direction of the stream of water in step 1 when you rotated the turntable?
  3. What happened to the direction of the streams of water in step 2 when you rotated the turntable with the 2 liter bottles clockwise? Counterclockwise? (You may want to sketch a drawing instead of writing it out).
  4. In step 3, the two bottles were placed against the wall of the container. What happened to the direction of the streams when rotated clockwise? Counterclockwise? (You may wish to sketch a drawing).
  5. When the turntable is rotating counterclockwise, the direction of the stream of water should be towards the right. This is analogous to the Northern Hemisphere of the Earth. If you lived in Africa, what direction would the direction of the stream of water turn? Why?

 
3. Sketch the pathway of the ball demonstrating the Coriolis Effect in the following website. Explain why the ball took the path it did.
http://www.geo.utep.edu/class_notes/3103_Miller/Lectures/Pressure_Wind/Coriolis.html
4. Go the following website to view a demonstration on the Coriolis Effect.
http://www.met.wau.nl:8888/courses/resource/nwp/n2200/

Once you reach that website, select the following file: Coriolis.mpg. Write a few sentences about what you observed.
5. Is the reason the water flows down a certain direction in a toilet bowl due to the Coriolis Effect? Explain why or why not?
http://people.ku.edu/~keithweb/640_2.html

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