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1-888-ABC-KNEX
1 Build the 1:1 Spur Gear model. Mark each
Gear near the rim with a small piece of tape.
Turn the crank for the top Gear one full turn
and observe the model.Which way does each
Gear move? How many turns did the bottom
Gear make? This Spur Gear model has a one
to one (1:1) gear ratio. Based on your obser-
vation, what does this mean?
(Refer to the
“What’s the Mechanical Advantage” Reference
Sheet for help.)
2
a.
Hang a cup with small weights (green Rods,
pennies, etc.) from the crank on the lower
Gear.Turn the top crank to lift the weight.
Feel how much force it takes to do this.
Connect the K’NEX Rubber Band Scale to
the end of the top Gear’s crank. Measure the
amount of force used to lift the weight.
Record your findings.
b.
Next, hang the weight from the crank for
the top Gear.Turn the lower crank and feel
the force used to lift the weight. Do you use
the same amount of force to lift the weight
now?
Measure the force used to lift the weight in
this position. Record your findings. Compare
the measurements. Did the amount of force
used differ? Why or why not? Write a para-
graph explaining your results.
3
a.
Build the 6:1 Spur Gear model. Repeat Ac-
tivity 1, turning the crank for the yellow Gear.
How many turns did the blue Gear make for
one turn of the yellow Gear? Based on your
observation, what is the gear ratio for this
model? Why would you need to use spur
gears that have different ratios?
b.
Repeat Activity 2, testing the weight on
each crank.Which Gear requires less force to
lift the weight? What are other benefits to
using this Gear arrangement?
4 Using K’NEX, build a hand cranked fan that
uses spur gears to turn at different speeds.
Make blades for your fan from cardboard or
poster board. Crank the fan and feel the cool
breeze!
1
1 Two adjacent spur Gears turn in opposite di-
rections. For the 1:1 Spur Gear, the bottom
Gear makes one turn as the top Gear makes
a single turn. A 1:1 gear ratio means that two
spur gears are the same size and they turn at
the same rate.
2. To lift weights with the 1:1 Spur Gear, you
need to apply the same force whether you
attach the weight to the top or bottom Gear
because the two Gears are the same size.
Same size gears turn with the same amount
of force.
a.
For the 6:1 Spur Gear, the small Gear turns
six times for each turn of the large Gear.
When spur gears differ in size, the smaller
one turns faster.
b.
Using the 6:1 Spur Gear, you need to apply
less force to the small Gear when the weight
is attached to the large Gear.The large Gear
turns more slowly, but with more force,
so you don’t need to supply so much force
yourself.
This arrangement changes the direction the
crank rotates.
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QUESTIONS
ANSWERS
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Summary of Contents for Education Simple Machines Deluxe GEARS
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