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(b) Describe the input motion (the motion you use
when you operate the crank).
(c) Describe the motion of the gears.
(d) Draw a diagram of the gear arrangement in your
notebook and use arrows to show the direction
each part moves as you operate the fan.
7. Attach a small piece of masking tape to the edge of
one fan blade and select a reference point so you can
keep track of the fan blade as it rotates.
(a) Turn the crank to make one rotation. Continue
turning the crank but vary the speed at which it
is turned. How can you make the fan turn faster/
slower?
(b) Mark the two gear wheels with either a dot sticker
or with a pencil mark. The marks should be made
at the point where the two gears mesh. Now turn
the crank one slow turn. What do you notice?
(c) Note in your notebook the sizes of the two gears -
driver and driven – used in the model.
(d) Could there be a relationship between the size of
the gears and your findings to (b)?
For printer friendly versions of the experiments, go to:
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(e) Turn the crank one additional turn, but this time,
notice how far the fan blades travel. Ask a friend,
parent, or teacher to count the number of times
the blade with the masking tape passes the
selected reference point, and focus on making just
one full turn with the crank.
(f) How easy/hard is it to turn the crank with this gear
arrangement?
(g) Summarize your observations concerning the
distance the two gears and the fan blades turn
with one rotation of the crank.
8. (a) What do you think will happen if you use:
(i) a large gear wheel to drive a small gear wheel &
(ii) a small gear wheel to drive a large gear wheel.
• Make a note of your responses in your notebook.
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