WIND
PATTERNS
Introduction
The Earth’s surface is rotating rapidly around the its axis. However, not all
parts of this planet rotate at the same speed. The parts of Earth near the
Equator rotate at a greater speed than those near the poles. This is
because a point on the Equator traces out a larger circle per day than a
point nearer either pole. A body traveling from a high latitude toward
the Equator tends to fall behind and veer to the west relative to the
more rapidly rotating equatorial regions. Similarly, a body traveling
toward either pole veers eastward because it retains the greater
eastward rotational speed of the lower latitudes as it passes over the
more slowly rotating Earth closer to the pole. This deflection of a body
due to Earth’s rotation is the Coriolis effect. In this experiment you will
simulate Earth’s wind patterns.
Time Needed
55 minutes
What You Need
F 1-hole rubber stopper
F string
F paper cup
F paper plate
F food coloring
F pencils
F science notebook
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WIND PATTERNS
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Safety Precautions
Please review and follow the safety guidelines.
What You Do
1. Cut a piece of string that is about 1 yard (1 meter) long.
2. Tie the string around the rubber stopper.
3. Holding the string so that the free end dangles through your fist,
spin the stopper above your head.
4. As you spin the stopper, pull the string through your stationary fist so
that the distance between your hand and the stopper shortens.
5. Observe the speed of the stopper as it gets closer to your stationary
hand. In your science notebook, describe any changes in the speed
of the stopper.
6. Use a pencil to punch a hole through the center of a paper plate and
through the bottom of a paper cup. Use the paper plate and cup to
construct the apparatus shown in Figure 1.
paper plate
with hole
and pencil
pencil
through plate
and cup
cup placed
upside down
for support
Figure
Figure 11
7. Place the apparatus on a table.
8. Hold the pencil securely and rotate the paper plate until it begins to
spin freely around the pencil.
Walker/Wood, Science Experiment, On File (JNEOF), Vol. 3, Fig 01(2.9-2)
9. Place several drops of food coloring in the plate, making a circle
of drops about 0.4 to 0.8 inches (in.; 1 to 2 centimeters [cm]) from
the pencil.
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WIND PATTERNS
10.
11.
Rotate the plate counterclockwise and observe the food coloring.
In your science notebook, draw your observations of the lines
created by the food coloring.
Observations
1. How did the rotational speed of the stopper change as
you shortened the length of the string?
2. How does the velocity of the stopper relate to the
velocity of air moving with the rotation of the Earth?
3. Based on this experiment, explain the Coriolis effect.
4. What explanation can you give for the pattern displayed
by the food coloring in steps 9 and 10?
Want to Know More?
See Our Findings.
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SAFETY PRECAUTIONS
Review Before Starting Any Experiment
GENERAL
• Always obtain your teacher’s permission for experiments performed
at school, and your parent’s permission for experiments performed
at home, before attempting any experiment.
• Read all instructions for an experiment before starting the
experiment, and follow the directions exactly as they appear in
this volume.
• If an experiment requires adult supervision, do not perform the
experiment unless you have an adult supervising you the entire
time you are performing the experiment.
• Wash your hands before the start of and after each experiment
you perform.
• Keep your work area clean.
• Never eat or drink while performing an experiment. Never taste a
substance used in an experiment unless you are told that it is safe
to do so.
• Be aware of the location of safety equipment you may need in an
emergency, such as running water, an eyewash if you are at school,
and a fire extinguisher.
• If you are going outside, make sure you have permission to go
from your teacher and parent. Take a buddy with you, and dress
appropriately for the weather. Make sure you or someone who
accompanies you is familiar with the area, and bring along a firstaid kit in case of emergency.
• Never look directly into the Sun.
CHEMICAL SAFETY
• Always wear goggles when working with chemicals, such as acids
and bases, and near heat sources like flames. If at all possible,
avoid wearing contact lenses when working with chemicals.
• If any substance gets into your eyes, notify an adult (e.g., your
teacher or parent) immediately, and flush your eyes with running
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water for at least 15 minutes. Do not mix chemicals unless you are
told to do so by a teacher or parent.
• Never touch, taste, or smell chemicals unless instructed to do so.
• Keep chemicals in closed containers when they are not in use.
• Dispose of all chemicals properly. Do not pour any chemicals or
solids down the drain unless instructed to do so.
• Use safety gloves and a plastic apron when handling chemicals. If
any chemicals spill on your skin, rinse the affected area with
running water for at least 10 minutes, and notify your teacher or
parent immediately.
• Take precautions to avoid spilling chemicals. If a chemical spills on
any surface, notify your teacher or parent immediately to assist
with clean-up.
• Exercise caution when using sharp instruments such as knives or
scissors. Always cut away from yourself, not toward yourself. If you
cut yourself, notify your teacher or parent immediately.
GLASSWARE
• Clean glassware when you are finished with the experiment.
• Be careful when using glassware. If a piece of glassware breaks,
have an adult assist you in clean-up to avoid injuries from broken
glass. Never use broken or damaged glassware.
FIRE SAFETY
• Do not heat glassware that is not completely dry. Do not pick up
hot glassware without heat-resistant gloves or tongs.
• When heating glassware, keep it away from yourself and from
others.
• Do not heat anything unless instructed to do so by a teacher or
parent.
• Do not heat substances in a closed container.
• After an experiment, make sure that all heating sources are off
and that all flames have been put out.
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SAFETY PRECAUTIONS
• Do not reach across such heating sources as flames.
• If you have long hair, tie it back, out of the way. Do not wear
clothing with loose sleeves, scarves, bows, ties, or anything else
that may hang into a fire. Do not wear long earrings.
ELECTRICAL SAFETY
• Do not touch electrical equipment when your hands are wet.
• Do not plug several electrical devices into one outlet or use an
extension cord.
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