1. Tractor Traction
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.

4. ENGAGING SCENARIO
In your previous investigation you discovered how a wheel and axle can work together to magnify force and make work easier. When we applied a force with the rubber band to our axle, the amount of force that was transferred to our wheels was so strong that the tractor car spun out and was not able to get traction with the ground. How could we modify or improve our cars so that friction would allow them to travel a greater distance (complete more work)?
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 we modify or improve the performance of our cars so they will travel a greater distance (complete more work)?
Previous Knowledge
Share experiences with traction related to objects that use wheels to roll.
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 _______________ because____________
If _____________________Then___________________
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6. Class Predictions (related to the focus question)

7. New Vocabulary Traction
Moving friction, the amount of contact between two surfaces necessary for one surface to travel across another.
Friction is normally the greatest enemy when completing work, but can it sometimes be beneficial?
How are the materials in the boxes organized? How can we find out the common property in each of the boxes?
How can we modify our cars to provide them more traction?

8. Preparing the Investigation
Do you think the tractor will go farther with or without rubber bands (tires) on its rear wheels? Adding Traction
What do you think will happen if we increase the level of friction between the car and the surface ?
What are we going to change
What are we going to keep the same
Traction vs. No Traction
Test with traction 3 trials
Test without traction 3trials
Traction vs. Increased Friction
Test with traction and sled 3 trials
Test without traction and sled 3 trials
wrap the rubber band around the axle three times.
start with the front wheels on the starting line.
distance traveled is the distance from the starting line to the point where the front wheels contact the floor when the tractor has come to a stop.

9. Collecting Data
Do you think the tractor will go farther with or without rubber bands (tires) on its rear wheels?
Tractor without Rubber Bands
Tractor with Rubber Bands
Trial #
Distance (cm) 1 2 3
Tractor without Rubber Bands and Hexnuts on a Sled
Tractor with Rubber Bands and Hexnuts on a Sled

10. Making Meaning Conference
Did adding traction to the wheels of the car increase or decrease the distance the car travelled?
Did attaching the sled with weight to the car increase or decrease the distance the car travelled?
Why did the increased traction of the wheels against the floor help the tractor to move farther, but the increased friction of the sled against the floor prevent the tractor from moving as far?
Do you think the results would be the same if we added another variable (different surfaces)?

11. Claims and Evidence
How can we modify or improve the performance of our cars so they will travel a greater distance (complete more work)?
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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