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LEGO, the LEGO logo and WEDO are trademarks of the/sont des marques de commerce de/son marcas registradas de LEGO Group. ©2009 The LEGO Group.
4. Hungry Alligator Teacher Notes
Students will build and program a mechanical alligator that makes sounds and is motorized to
open and close its jaw.
Objectives
Science
Trace the transmission of motion and transfer of energy through the machine.
Identify the pulleys and belts and the slowing down mechanism at work in the model.
Consider the needs of living animals.
Technology
Create a programmable model to demonstrate the knowledge and operation of digital tools and
technological systems.
Engineering
Build and test the alligator’s movement.
Improve the alligator’s behavior by adding the motion sensor and programming sounds to
coordinate with the movement.
Mathematics
Understand how the distance between an object and the motion sensor is important to how the
sensor functions.
Understand and use numbers to represent the type of sounds played and the amount of time the
motor turns on.
Language
Prepare and deliver a demonstration about alligators using the alligator model.
Use technology to create and communicate ideas.
Communicate in spoken or written forms using the appropriate vocabulary.
Vocabulary
Belts, motion sensor, and pulley. Blocks: Motion Sensor Input, Motor On For, Motor This Way, Motor
That Way, Number Input, Play Sound, Repeat, Start On Key Press and Wait For.
Other Materials
Optional for Extension: Construction paper, cardboard, grass, rocks.
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4. Hungry Alligator Teacher Notes
LEGO, the LEGO logo and WEDO are trademarks of the/sont des marques de commerce de/son marcas registradas de LEGO Group. ©2009 The LEGO Group.
Connect
Review the Connect animation and discuss:
What was the alligator doing when Mia and Max saw it?
What happened as they stood near the alligator?
Do alligators really eat caps?
Why does an alligator have a large jaw?
What kind of food does an alligator eat?
Would you pet an alligator? Why or why not?
Here are other ways of connecting:
Pretend you are an alligator. How does an alligator walk? Use your arms to show how the alligator
opens and closes its jaw.
Have you seen a real alligator in person or on television? What did it do?
Is an alligator like a dinosaur? Why or why not?
Alligators lived as far back as some dinosaurs. However, dinosaurs are extinct, alligators are
not. Alligators are reptiles: they lay eggs, have scales on their skin, and are cold-blooded. Coldblooded means they must use the sun and means outside their body to stay warm. Dinosaurs
seemed to have had these traits also.
Did you know…
You can use belts and pulleys to slow down the motor speed?
See the model in Getting Started:
9. Decrease Speed.
How much slower is the large pulley than the small pulley?
The large pulley turns only one time for every three times the small pulley turns. The large pulley
is three times slower than the small pulley
4. Hungry Alligator Teacher Notes
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LEGO, the LEGO logo and WEDO are trademarks of the/sont des marques de commerce de/son marcas registradas de LEGO Group. ©2009 The LEGO Group.
Construct
Build the model following step-by-step instructions or create your own alligator. If you create your
own, you may need to change the example program.
To operate the alligator best, make sure the jaw opens and closes easily. To do that, loosen the
pulleys and bushings to reduce friction. If the belts have been used a lot, wipe them clean to
improve performance.
The energy transfers from the computer powering the motor, to the crown gear at a 90° angle to
the next gear. That gear turns a small pulley and a belt that are on the same axle as the gear. The
belt connects the small pulley to the large pulley. Moving the large pulley opens and closes the
alligator’s jaw.
The energy changes from electrical (the computer and motor) to mechanical (physical movement
of the gears, belts and the jaw mechanism).
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