TESLA Simple Machines 2010

Gears

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.

Knowledge We Will Build on From Prior Investigations

Work = Distance X Force

Force is a push or pull applied to an object.

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.

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?

Discuss ideas with a partner for a possible focus question. Your focus question should be connected to what the scenario wants us to do…

Focus Question (What is the problem?)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?

Prediction (related to the focus question) Prediction (related to the focus question)

Prediction:I predict that a gear can be used to make work easier by… because____________

Prediction:I predict that a gear can be used to make work easier by… because____________

Previous Knowledge Previous KnowledgeShare experiences with gearsShare experiences with gears

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Class Predictions (related to the focus question) Class Predictions (related to the focus question)

What do you think is happening inside this system?

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New VocabularyNew Vocabulary

Gear• A special type of wheel that has evenly spaced teeth around the edge. Gears

can transfer force from one to another

Driven Gear:The driven gear is a gear that receives force

Driving Gear: A driving gear is a gear that transmits force to another gear

If you rotate the driving gear one full revolution, what happens to the driven gear?

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New VocabularyNew 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 :

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 teethDriving gear has 30 teeth

Collecting DataCollecting Data

Remember… Gear Ratio is always Driving : Driven

What is the mechanical advantage to using 3 or more gears?

Making Meaning ConferenceMaking Meaning Conference

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 are gears? • What is the difference between a driving and 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?

Claims and EvidenceClaims and Evidence

I claim that… I claim this because…

How can gears be used together to make work easier?

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Reflection/ConclusionReflection/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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