TESLA Simple Machines 2010

Tractor Traction

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.

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?

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 we modify or improve the performance of our cars so they will travel a greater distance (complete more work)?

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

Prediction:I predict that _______________ because____________If _____________________Then___________________

Prediction:I predict that _______________ because____________If _____________________Then___________________

Previous Knowledge Previous Knowledge

Share experiences with traction related to objects that use wheels to roll.Share experiences with traction related to objects that use wheels to roll.

NOTEBOOK ENTRY

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

New VocabularyNew Vocabulary

Traction• Moving friction, the amount of contact between two surfaces

necessary for one surface to travel across another.

How can we modify our cars to provide them more traction?

Friction is normally the greatest enemy when completing work, but can it sometimes be beneficial?

Preparing the InvestigationPreparing the InvestigationDo you think the tractor will go farther with or without rubber bands (tires) on its rear wheels? Adding Traction

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

Traction vs. No TractionTest with traction 3 trialsTest without traction 3trials

Traction vs. Increased FrictionTest with traction and sled 3 trialsTest 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.

What do you think will happen if we increase the level of friction between

the car and the surface ?

Collecting DataCollecting 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) Trial # Distance (cm)

1 1

2 2

3 3

Tractor without Rubber Bands and Hexnuts on a Sled

Tractor with Rubber Bands and Hexnuts on a Sled

Trial # Distance (cm) Trial # Distance (cm)

1 1

2 2

3 3

Making Meaning ConferenceMaking Meaning Conference

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?

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?

Do you think the results would be the same if we added another variable (different surfaces)?

Claims and EvidenceClaims and Evidence

I claim that… I claim this because…

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

NOTEBOOK ENTRY

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…

NOTEBOOK ENTRY