TESLA Simple Machines 2010

Friction

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.

ENGAGING SCENARIO

Many of the tasks (work) that need to be completed involve moving an object from one location to another. To complete the work you must move the object with force, a certain distance.

Work = Force X Distance.

When we are moving objects from one location to another, friction often plays a major role in increasing the force required to complete the work. In this investigation you will need to gather and provide evidence of how friction can affect the amount of force needed to complete a task (work).

• 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 friction affect the amount of force needed to complete a task (work).

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New VocabularyNew Vocabulary

Friction:A force that resists motion whenever the surfaces of two objects rub against each other.

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Try rubbing your hands together hard and fast… What happens?

The friction between the two surfaces causes heat.

Now look at the bottom of your chair and the carpet, do you see signs of wear from these two surfaces rubbing together?

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

Prediction:I think that friction will/will not affect the amount of force needed to move an object because _______________.

Prediction:I think that friction will/will not affect the amount of force needed to move an object because _______________.

Previous Knowledge Previous Knowledge

Share experiences with friction related to the focus question.Share experiences with friction related to the focus question.

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

Preparing the InvestigationPreparing the InvestigationWe are going to test the force and work required to move a brick across three different surfaces. Each group will be given a spring scale, 1 brick, a meter stick, and three surfaces. (wood, wax paper, and sandpaper)

What are we going to change What are we going to keep the same

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The surface we pull the object across

• The object: brick• The spring scale• The distance we pull the object

Collecting DataCollecting Data

We need to keep track of our data and observations…

Work on Three Different Surfaces

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Making Meaning ConferenceMaking Meaning Conference

Why do you think the brick moved most easily across this surface?

Which of the three surfaces required you to do the most work?

Why do you think more force was required to move the brick across this surface?

On which surface did the brick display the most friction? Explain.

On which surface did the brick display the least friction? Explain.

On which surface was the brick easiest to move?

Is there a way we could decrease the amount of friction on all three surfaces?

Claims and EvidenceClaims and Evidence

I claim that… I claim this because…

How can friction affect the amount of force needed to complete a task (work).

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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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