KNEX Education Simple Machines Deluxe GEARS, Руководство для учителей

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1.
Carefully, or with the help of an adult,
start your Worm Gear model by plugging
the cord into the gray K’NEX Motor.
Watch theWorm and theWorm Gear
turn.Which way do they move? Draw a
picture with arrows to show the direction
that each part turns.
2
a.
Watch the Worm turn.You can see that
it spins very fast! Then, watch the Worm
Gear turn and have a partner help you
count the number of times it turns in 60
seconds. Mark one spot with tape or a
marker so you can easily tell when the
Worm Gear makes a full rotation. Divide
the number of turns by 60.Your answer
will be the number of turns the Worm
Gear makes per second.Write down
your answer.
b.
Next, count and record the number of
teeth on the Worm Gear.
c.
Every time the Worm turns one full
turn, the Worm Gear moves ahead the
distance of only one small tooth. For the
Worm Gear to make one full turn, the
Worm has to turn the same number of
times as the number of teeth on the
Worm Gear.That means the Worm
turns fast! To find out how fast, try this
multiplication problem.
Your answer will be the number of turns
the worm makes per second.That’s fast!
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* CAUTION: Supervise students when
they use the K’NEX Motor. Plug the
transformer into the wall yourself and let
them connect the small plug to the Motor.
Make sure the Motor is not used near
water and that students have dry hands
when handling the plug.
1. Worm gears change the direction of
motion. Like bevel or crown gears, the
worm turns in one plane and the worm
gear in a plane at right angles to that of
the worm.To help students visualize this
motion, ask them to look head on at the
Worm, to see it as a wheel.Then, they
should see that the two “wheels” — the
Worm and the Worm Gear — are at right
angles to each other.Their drawings
should reflect this arrangement.They
might draw axles through the wheels to
better reflect the right angle.
2
a.
The Worm moves so fast it’s almost
impossible to count the turns. However,
the Worm Gear moves slowly enough
that they can count how many turns
it makes in a minute. Use this observation
to reinforce the idea that worm gears can
be used to reduce speed (or increase
speed, if the worm gear makes the worm
turn). Students will probably find that the
Worm Gear turns about 90 times in 60
seconds or about 1.5 times per second.
b.
The Worm Gear has 50 teeth.
c.
The number of turns the Worm makes
per second is: 1.5 turns per second x 50
teeth per turn = 75 turns per second.
Note that this speed is much faster than
the 1.5 turns per second of the
Worm Gear.
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2
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ANSWERS
QUESTIONS
Number of turns
per second
X
Number of worm
gear teeth
1-888-ABC-KNEX
WARNING:
Important note: Be extremely
careful whenever using electrical devices.
Teachers should monitor student activities at all
times, and should examine devices before use.