Round and Round We Go

Purpose: To simulate the Coriolis Effect

Materials

• rotating platform such as a Lazy Susan
• aluminum pie pan
• food coloring
• water
• paper cup
• pushpin
• crushed ice
• science journal

Background
The entire Earth makes one complete turn around its axis every 24 hours. Since the Earth is a sphere, the surface of the Earth moves about 1,600 km/hr faster at the equator than it does at the poles where the speed is nearly 0 km/hr. Imagine yourself on a merry-go-round spinning around very fast. It is more difficult to hang on when you are near the outer edge of the merry-go-round. If you move toward the center of the merry-go-round, it takes virtually no effort at all to hang on because the outer edge is moving much faster than the center-most part.

Procedure

1. Place the pie pan on the Lazy Susan and fill with water to within 1-2 cm from the top.
2. Using a pushpin, put four small pinholes approximately 1 cm from the base of the paper cup. Space the holes equally around the cup.
3. Fill the cup 1/2 to 2/3 full of crushed ice.
4. Place the cup in the center of the pie pan.
5. Begin to turn the Lazy Susan in a counterclockwise direction to simulate the Earth's rotation. Be sure to keep the platform rotating slowly and constantly.
6. Have your partner add several drops of food coloring to the cup.
7. Add a small amount of water to the cup.
8. Observe and write your observations in your science journal.
9. Stop the spinning of the Lazy Susan and observe.
10. Write your observations in your science journal.

Conclusion

1. Describe the motion of the food coloring as it came out of the cup as the Lazy Susan was spinning.
2. How does this motion describe the Coriolis Effect?

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Answer Key

1. Describe the motion of the food coloring as it came out of the cup when the lazy Susan was spinning.

The food coloring curved as it came out of the holes in the cup.

2. How does this motion describe the Coriolis effect?

This deflection of the food coloring is similar to that of large air masses on the surface of the Earth. As the Earth rotates, the spinning deflects air in a counterclockwise direction in the Northern Hemisphere.