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Level Four > Geometry and Measurement

Chilling Out

Purpose: 
This is a level 4 measurement strand activity from the Figure It Out series.
Achievement Objectives:

Achievement Objective: GM4-4: Interpret and use scales, timetables, and charts.
AO elaboration and other teaching resources

Specific Learning Outcomes: 

construct and use an anemometer

Required Resource Materials: 
FIO, Level 4+, Measurement, Book Two, Chilling Out, page 24
a large protractor, nylon line, table tennis ball, an OHT pen
glue or glue gun, cardboard
windt days
Activity: 

In this activity, the students make a simple anemometer using everyday materials such as a table tennis ball, protractor, and cardboard. There is no reason why everyone in the class can't use the one large protractor.
The students can draw its outline on the card, transfer the data from the table in the book to the outline, and then pass the protractor on to someone else. The figures in the table convert the degrees on the protractor into very approximate wind speeds.
The students may find that the best way to attach the nylon line to the table tennis ball is to thread it through the ball on a long needle and then knot it on the far side. They need to attach the other end of the line to the centre of the protractor. The students use the completed anemometer to record the wind speed over several days.
To use the anemometer, one student holds it so that the baseline (the 0 - 180 degree line) is horizontal and aligned with the direction of the wind. A second student observes and records where the line crosses the wind-speed scale. If the line is moving up and down, they should read the mid-way value.
It is best if the wind is blowing steadily when measured. In gusty conditions, the ball will blow all over the place and the students will not be able to get a consistent  reading.


Investigation

Using the Internet, the students will discover that the wind chill factor concept has undergone a major overhaul in recent years. This is because the early tables did not adequately reflect the way people experience cold and wind. A useful introduction can be found at: http://www.nws.noaa.gov/os/windchill/index.shtml
The formula now used to calculate wind chill looks extremely scientific and accurate, but it is only a model.  Some authorities doubt its value.


Cross-curricular links

Science
This activity could be used as part of a unit on weather measurement and observation. The students could design and make other weather instruments, such as a barometer, windsock, or weathervane, and then use them to record and forecast the weather, keeping a record of the accuracy of their predictions. This unit could also make use of the weather maps found in the daily newspaper.


Achievement Objective

  • investigate major factors and patterns associated with weather, and use given data to predict weather (Making Sense of Planet Earth and Beyond, level 4)

Answers to Activity

1. Practical activity
2. Answers will vary.
Investigation
Answers will vary. You should discover that the wind chill factor can never make something colder than the air temperature. (No matter how severe the wind, water
will not freeze if the air temperature is above 0oC.) What the wind chill factor does do is greatly speed up the cooling process. This means that hypothermia can
set in much more rapidly, before a person has had time to realise the danger. If the conditions make hypothermia a risk, you should wear warm clothes (including a hat), keep dry, and if possible, keep out of the wind.