21
a.
Set up the Sprocket Bicycle Gear model with
the chain wrapped around the two sets of small
yellow Gears.Turn the pedal and count the num-
ber of times the Wheel turns. Record your an-
swer. What is the gear ratio for these Sprocket
Bicycle Gears? What is the Mechanical Advantage?
(Refer to the “What’s the Mechanical Advantage”
Reference Sheet.)
b.
Attach a cup with small weights to the gray Rod
with the Wheel. Measure the force used to turn
the pedals with the K’NEX Rubber Band Scale.
(Snap the orange Connector at the bottom of the
Scale to the blue Rod on the pedal.) Record your
results.
2
a.
Add extra links to the Chain.Wrap the Chain
around the set of small Gears and big Gears. Now
put the pedals on the axle with the small Gears.
Put the wheel on the axle with the big Gears.
How does it feel to turn the pedals?
b.
Repeat the process from Activity 1. Compare
these results with your previous results.Which
set of Sprocket Bicycle Gears need more force to
lift the weight? Why?
3
a.
Now switch the pedals to the axle with the big
Gears, and put the Wheel on the axle with the
small Gears.Turn the pedals. How does it feel?
Does the Wheel turn faster or slower? Why?
b.
Repeat the process from Activity 1.
4 Compare all your results.Why are the gear com-
binations described as high and low? How do
your force and speed measurements prove this?
Which Gear arrangement lets you ride fast with
the least force? Explain.
6 Why are sprocket gears a good choice for a
bicycle? Make a list of machines that use sprocket
gears. Explain why this gear system is the best
choice for these machines.
1
1
a.
The gear ratio for the set of small Sprocket Bi-
cycle Gears is 1:1.They turn in the same direc-
tion. The Mechanical Advantage is 1.
2
a.
Students should find that they must turn the
pedals (which are attached to the small Gears)
about 2.5 turns for every turn of the wheel
(which is attached to the large Gears).The pedals
turn easily, but the wheel doesn’t go very fast.
b.
Students will find that it takes less force to lift
the weight when turning the small Gears to make
the large Gears lift the weight.This arrangement
has a MA of 2.5.
3
a.
They only need to turn the pedals (which are
attached to the large Gears) less than one-half a
turn (about 0.4 turn) for the wheel (which is at-
tached to the small Gears) to turn once.The ped-
als are harder to turn, but the wheel turns faster.
b.
Students will find that it takes more force to lift
the weight when turning the large Gears to make
the small Gears turn but the weight is lifted faster.
This arrangement has a MA of 0.4.
4. With the K’NEX model set in low gear it’s easier
to pedal faster because you don’t need to apply a
lot of force. However, you do not go very far be-
cause the wheel does not turn very often.With
the model in high gear, you must apply more
force. It will be more difficult to turn the pedals
but they will turn the wheel much more often, to
go farther.
The K’NEX model correlates to a real bicycle: the
bicycle’s front gears are attached to the crankshaft,
which the pedals turn.The back gears are attached
to the back wheel, so they turn with the wheel.
5. Sprocket gears make a good choice for a bicycle be-
cause the chain makes the pedal gear turn in the
same direction as the wheel gear.The chain allows
the pedal gear and the wheel gear to be separated
from each other so you have room for the pedals
and your legs.
Students may have seen sprocket gears in chain
saws, chain hoists, garage door openers, barbecue
rotisseries, movie projectors and cameras (the
film acts as the “chain”).These machines use
sprocket gears to move the chain or to turn a
gear some distance away.
1
2
2
3
3
ANSWERS
5
QUESTIONS
4
4
5
1-888-ABC-KNEX
Summary of Contents for Education Simple Machines Deluxe GEARS
Page 1: ......
