1. Gears
TESLA Simple Machines 2010

2. The Big Idea of this Investigation
A simple machine is a mechanical device that makes work easier by magnifying, modifying, transferring, or changing the direction of applied force. Simple machines are the elementary "building blocks" of which all complicated machines are made.

3. Knowledge We Will Build on From Prior Investigations
Force is a push or pull applied to an object.
Work = Distance X Force
Friction is the number one enemy of simple machines. It increases the amount of force needed to do work.
Wheels reduce the amount of friction between an object and the surface over which it moves.
A wheel and axle can work together to magnify force and make work easier. When a large wheel is attached to a small axle the same amount of work can be completed with less force by turning the wheel.

4. ENGAGING SCENARIO
In previous investigations we continue to discover how simple machines can make work easier. A gear is a special type of wheel with teeth. In this investigation we need to find out how a gear can be used to make work easier by magnifying, modifying, transferring, or changing the direction of applied force.
What is the problem we need to solve?
What do we need to investigate?
Teachers need to show the boxes to help students understand the situation. Review the clues in the engaging scenario by asking questions: how many boxes?, how are they organized?, why do we need to know how they are organized?
Discuss ideas with a partner for a possible focus question. Your focus question should be connected to what the scenario wants us to do…

5. Focus Question (What is the problem?)
How can gears be used to make work easier by magnifying, modifying, transferring, or changing the direction of applied force?
Previous Knowledge
Share experiences with gears
How are the materials in the boxes organized? How can we find out the common property in each of the boxes?
Prediction (related to the focus question)
Prediction:
I predict that a gear can be used to make work easier by… because____________
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6. Class Predictions (related to the focus question)
What do you think is happening inside this system?
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7. New Vocabulary
Gear
A special type of wheel that has evenly spaced teeth around the edge. Gears can transfer force from one to another
Driving Gear:
A driving gear is a gear that transmits force to another gear
Driven Gear:
The driven gear is a gear that receives force
How are the materials in the boxes organized? How can we find out the common property in each of the boxes?
If you rotate the driving gear one full revolution, what happens to the driven gear?
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8. New Vocabulary Gear Ratio:
The relationship between the number of rotations of each gear.
It is written as a fraction or ratio
# Rotations of the driving gear / # Rotations of the driven gear
For Example
1/3 or 1:3  :
How are the materials in the boxes organized? How can we find out the common property in each of the boxes?
1 Rotation
Driving Gear
3 Rotations
Driven Gear
Why do you think the driven gear rotated three times for every rotation of the driving gear?
Driven gear has 10 teeth
Driving gear has 30 teeth 8

9. Collecting Data Remember… Gear Ratio is always Driving : Driven
What is the mechanical advantage to using 3 or more gears?

10. Making Meaning Conference
What are gears?
What is the difference between a driving and driven gear?
When using only 2 gears which direction does the driven gear turn if the driving gear is turned clockwise?
How can you change the direction of the driven gear?
What does it mean if your system has a 1:4 gear ratio?
If you driving gear has 40 teeth, how many does your driven gear have?
How can gears be used together to transfer force?
How can gears be used together to change or magnify force?

11. Claims and Evidence
How can gears be used together to make work easier?
I claim that…
I claim this because…
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12. Reflection/Conclusion
Revisit your original prediction… Explain how the evidence did or did not support your original prediction?
My prediction was accurate because…..
I wish to revise my prediction because…
What did you learn…
What really surprised you…
What new questions do you have…
What would you like to know more about…
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