CHAPTER INVESTIGATION
Wind Power
OVERVIEW AND PURPOSE Early windmills were used
mainly to pump water and grind flour. In this lab, you will use
what you have learned about renewable resources to
• build a model windmill and use it to lift a small weight
• improve its performance by increasing the strength of
the wind source
Problem
Write
It Up
What effect will increasing the wind strength have on the lifting
power of a model windmill?
Hypothesize
• half of a file folder
• metric ruler
• quarter
• scissors
• paper punch
• brass paper fastener
• drinking straw
• pushpin
• masking tape
• small paper clip
• pint carton
• 30 cm of string
• clock or stopwatch
• small desktop fan
It Up
After completing step 8 of the procedure, write a hypothesis to
explain what you think will happen in the next two sets of trials.
Your hypothesis should take the form of an “If . . . , then . . . ,
because . . .” statement.
Procedure
Make a data table in your Science Notebook,
like the one on page 323.
Cut a 15 cm square from a manila file
folder. With a ruler, draw lines from the
corners toward the center, forming an X.
Where the lines cross, use a quarter to
draw a circle. Cut inward along the lines
from the four corners, stopping at the
small circle. Punch a hole in each corner
and in the center of the circle.
15 cm
MATERIALS
Write
step 2
Bend the cardboard to align the holes.
Push a brass paper fastener through the holes
toward the back of the pinwheel. Do not
flatten the metal strips of the fastener.
Use a pushpin to poke a hole through a
straw, about 4 cm from the end. Then push
the metal strips through the hole and flatten
them at right angles to the straw. Fold the
tip of the straw over and tape it to the rest
of the straw.
322 Unit 2: Earth’s Surface
step 4
Cut the spout portion off the top of the pint
carton. Punch two holes on opposite sides of the
carton. Make sure the holes line up and are large
enough for the straw to turn easily.
Write
Conclude
It Up
1. INTERPRET Answer the question posed
under “problem” on page 322.
Slide the straw through the holes. Tape the string
to the end of the straw. Tie a small paper clip
(weight) to the other end
of the string.
hypothesis?
3. IDENTIFY LIMITS What limitations or
sources of error could have affected your
experimental results?
Test the model by
blowing on the
blades. Describe
what happens to
the weight.
4. APPLY Wind-powered turbines are used
to generate electricity in some parts of the
country. What might limit the usefulness of
wind power as an energy source?
Run three trials of the
step 6
lifting power of the
model windmill as you
blow on the blades. Keep the amount of force
you use constant. Have a classmate use a stopwatch or clock with a second hand to time the
trials. Record the results in your data table.
Average your results.
Vary the strength of the wind by using a
desktop fan at different speeds to turn the
windmill’s blades. Remember to record your
hypothesis explaining what you think will
happen in the next two sets of trials.
Observe and Analyze
2. ANALYZE Did your results support your
Write
It Up
1. MODEL Draw a picture of the completed
windmill. What happens to the weight when
the blades turn?
2. IDENTIFY VARIABLES What method
did you use to increase the wind strength?
Add a sketch of this method to your picture
to illustrate the experimental procedure.
3. RECORD OBSERVATIONS Make sure
your data table is completed.
4. COMPARE How did the average times
it took to raise the weight at different
wind strengths differ?
INVESTIGATE Further
CHALLENGE How you can get your model
windmill to do more work? You might try different weights, or you might build a larger windmill
and compare it with your original. Create a new
data table. Use a bar graph to compare different
weights and wind strengths. How much wind
power is needed to lift the additional weight?
Wind Power
Problem
Hypothesize
nalyze
Observe and A
Lift Weight
Table 1. Time to
e (sec)
Trial Number Tim
Wind Force Used
1
Student powered
2
3
Average
1
Fan on low
2
speed
3
Average
1
Fan on high
2
speed
3
Average
Conclude
Chapter 9: Natural Resources 323