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# THE NEED FOR SPEED

Learning Intention:

To understand the measurement of wind. To learn how to use an anemometer and record and analyse data.

NIWA and Emirates Team New Zealand. Thanks to NIWA for the video

Discussion:

Have you been outside in a really strong wind?

Wind can blow at gentle speed or so strong it can cause damage.  Wind speed is the measurement of how fast the air is moving.

How can something be measured when you can’t see it?

How do we measure wind?

Meteorologists often test wind speed using a tool called an anemometer.  It is a pole with cups on top.  The wind blows into the cups which make them spin.  You can figure out the speed of the wind by counting how many times the cups spin over a set time period.

What is the unit of measure for wind speed?

In Aotearoa, wind over land is measured in kilometers per hour (km/h).  Wind over water is measured in knots, which is a nautical mile per hour.

What are some words we use to describe wind speed?

A gentle breeze, gusty, stormy, strong winds, light winds, blustery, stiff, violent, gale-force

How can we make an instrument to measure speed?

Activity:  Design, make and test an anemometer then record wind speed.

Use the materials listed below to design, build and test an anemometer.

Materials:

• Ruler

• 4 paper cups (recycled coffee cups)

• Marker

• Scissors

• Straw - preferably paper

• Wooden skewer

• Stapler or hot glue gun

• Heavy card - cardboard from a recycled box works well

• Fan (not necessary if you only want to test outside)

• Stopwatch (not necessary if you count the seconds)

• Ice block sticks. Maybe necessary prevent cardboard bending.

Procedure:

1. Decorate the outside of one cup with a marker.  This is the cup children watch so they can count the number of rotations.

2. Cut two equal sized strips of cardboard: approximately 2.5cm wide x 25-30 cm long.

3. Use hot glue or stapler to connect the strips to form a 'corss'. (Not directly in the centre, as that space is needed for the skewer).

4. Staple or hot glue a cup, turned sideways, to each end of the strips; cups all facing the same direction.

5. You can glue ice block sticks to the back of each strip if they are floppy.

6. Push the pointy end of the skewer through the centre of the cardboard frame.  (You may need to poke with a drawing pin first)

7. Thread the straw onto the skewer below the cups.

8. Hold the straw for testing.

9. Test by blowing on cups to see if they turn easily.

Test with a fan:

1. While holding the anemometer in front of the fan on low, count how many times the marker cup goes by in one minute.  This is the number of rotations per minute or rpm.

2. Record on a chart the number of rpm for four trials. Calculate the average rpm.

3. Compare your average rpm from the fan on low with other student's rpm. Was their difference between anemometers? If so, why?

4. Find the class average (sum of rpms divided by number of anemometers tested), median (middle number), and mode (most often occurring number).

Testing outside:

Use your anemometers to measure wind speed in several locations.

Work in pairs with one anemometer.  Each pair picks four locations on the school grounds to collect wind speed.

First make predictions about the wind strength in each location.  Will they have higher or lower wind speeds?  Why did you make these predictions?

Assign roles: One person is the Counter, who holds the anemometer and keep track of time. Each measurement should be for a 30 second period.  The other person is the Recorder, who counts the number of rotations - how many times the coloured cup goes round - and records on a piece of paper. Multiply rotations by 2 to get the total rotations per minute.

Take three recordings at each location and calculate the average rotation at each location.  Now draw conclusions about the data collected.  Were your predictions correct?  Why do wind speeds vary between the locations and what may have caused a difference in the readings.

Analyse the class data.  Did any of your classmates record the wind speed in the same place as your group?  Did they get the same results?  Why or why not?  Did some anemometers work better than others? What was different about them?

Glossary:

Wind, Kōkōhau - Moving air

Ocean, Moana

Sailboat, Waka Hourua

Tāwhirimātea - The Atua or god of weather including the god of wind.  He is the son of Papatūānuku (earth mother) and Ranginui (sky father)

Meteorologist - A weather scientist

Oceanographer - Someone who studies the ocean

Anemometer - An instrument for measuring wind speed

Wind Vane - A device that measures the direction of the wind

Weather Prediction - What you think will happen with the weather

Sea buoy - A floating marker in the sea

Knot - One nautical mile per hour

Compass - A tool for finding direction such as North, South, East or West

Sea Breeze and Land Breeze - The winds created by a difference in temperature between the sea and the land

Prevailing Wind - The most common wind in a location

Sea State - The height of the waves

Wind Rose Diagram - A diagram that summarizes information about the wind at a particular place and over a period of time

Ocean swell, Hone - A long rolling wave that is formed a long way away

Wind Turbine, Kapohau - A propeller that gets spun by the wind to turn wind power into energy

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