# Experiment: Which surface creates the most friction

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## Objective

SWBAT work through the steps of the scientific method to determine which surface creates the greatest amount of friction.

#### Big Idea

Students act as scientists to conduct an experiment to test if wood, cardboard, burlap, or carpet produce the greatest amount of friction for a toy car.

## Rationale and Preparation

The Why Behind Teaching This:

This unit covers standard 5-PS2-1: Support an argument that the gravitational force exerted by Earth on objects is directed down.  During the unit, students will investigate a variety of objects to see that the force of gravity is constant on Earth and pulls things down towards its center.  We will also be investigating a variety of ways to overcome gravity.

Several of the lessons in this unit are engineering design projects requiring students to follow the steps of the engineering design process to construct a project.  These projects address standard 3-5-ETS1-1: Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost. It also addresses engineering standard 3-5-ETS1-2: Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem. This specific lesson is an experiment requiring students to control variables which addresses standard 3-5-ETS1-3:Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

This specific lesson addresses standard 5-PS2-1 by relating the downward motion of a toy car to the pull of gravity.  We discuss in the lesson that the force opposing gravity is friction with the surface.  As we test each surface, we determine if any create enough friction to overcome gravity and stop the car before it travels all the way down the ramp.

Lesson Goal:

The goal of this lesson if for students to demonstrate an understanding that different surfaces produce different amounts of friction.

Success Criteria:

Students will demonstrate success on this lesson by using data collected in the experiment to write a conclusion stating which surface produced the most friction.

Preparing for Lesson:

Warm Up:

• Computer to show video

Guided Practice:

Explore:

• 3 books per group
• 1 ramp for each group
• piece of wood the same size as the ramp for each group
• piece of cardboard the same size as the ramp for each group
• piece of burlap the same size as the ramp for each group
• piece of carpet the same size as the ramp for each group
• 1 toy car for each group
• 1 measuring tape for each group

Wrap Up:

• Markers for creating graphs

## Warm Up

5 minutes

A Friction Experiment

I show a quick YouTube video to begin today's lesson. The video discusses how different surfaces create different amounts of friction.  We will be testing different surfaces in our experiment today so this video leads into the lesson nicely.

After watching the video.  I tell students that we will be testing how different surfaces affect the motion of a toy car today.  In the video they test concrete, grass, and carpet.  We will be testing wood, cardboard, burlap, and carpet.

## Guided Practice

20 minutes

Experiment Set Up in Notebooks

Students take out their science notebooks and glue in a prefolded, trifold paper I pass out.  I place my science notebook on the overhead to use as a visual for students.  Having the visual up for students to use helps the ESE and ELL students as well as those students who struggle with writing and spelling.

I provide the ESE students with a copy of the Friction Experiment Steps that have been precut and put into a baggie for them.  Having these steps available allows them to focus on the discussion taking place and not just on copying information down.  I have the other students write the steps because they are quicker at writing and by hearing it, reading it, and writing it, it may help them retain the information more easily.  The steps that are provided to the ESE students have been cut out so that they still have to read the information, decide where it belongs, and glue it in the correct location.  This allows them to hear the information and read the information.

We record the question: Which surface creates the greatest amount of friction? I show students the wood, cardboard, burlap, and carpet surfaces that they will be testing.  I allow students to feel the surfaces and discuss the differences with their group.  In order to make a hypothesis, students will need to use their observations to determine which they believe will produce the most friction.

After feeling each of the surfaces, I begin the hypothesis as: If I release a toy car on a ramp with a wood, cardboard, burlap, or carpet surface, then I predict ____________________________. I instruct students to complete the sentence with what type of surface they believe will produce the most friction.  Before recording their hypothesis, I ask what will happen with the surface that produces the most friction.  Students tell me that the car will not travel very far.  I do this as a review of what we learned about friction in the Types of Forces lesson at the beginning of the unit, as well as knowledge they should have obtained from the video.

We record the materials that are needed for the experiment: 3 books, ramp, cardboard, wood, burlap, carpet, toy car, and measuring tape.  I then pass out a copy of the Friction Experiment Procedure to each student.  The ESE students already have this with their other steps, but I provide it to everyone else as a way to save time.  There are several steps in the experiment which would take an extended amount of time to copy.   As I read through the steps, we discuss the forces acting on the car.  When the car is placed at the top of the ramp, gravity is the only force that should act on the car.  I point out that no students should be applying a force by pushing the car.  I ask students what force acts against gravity as the car rolls down the ramp.  They tell me friction.  I explain that as we test each surface, we will see if any of the surfaces produce enough friction to overcome the force of gravity and stop the car before it moves down the ramp.

The final step in setting up the experiment is to create a data chart.  The data chart goes in the middle of the foldable.  It is made up of 4 columns, one for each trial, and the headings. There are 5 rows, one for each surface and the last for headings.

inside of ramp foldable

Identifying Variables

Being able to identify the variables in an experiment and knowing how to control those variables is an important aspect of experimentation.  On the front cover of the experiment foldable, we record the following information and discuss.

• Independent Variable - type of surface
• Dependent variable - distance traveled (I stress that we are measuring the distance traveled, not the speed of the car)
• Control Variables - height of ramp, length of ramp, car used, how you measure (from front of car or back), force used to move the car.

front cover of foldable

## Explore

25 minutes

Conducting the Experiment

I have table groups set up with one high level student, one student on grade level, and two struggling students.  This set up works well for an ESE inclusion room because it allows the ESE students to get support in working through the steps from their peers.  They are often more comfortable asking for help from a peer, in a small setting such as group work.

I call one student over from each group to be the materials manager.  This student is responsible for getting all materials for the experiment, keeping them organized during the experiment, and returning them following the experiment.  Once they receive their materials, groups spread out around the room and set up their ramp to begin testing.

Students spend the next 20 minutes conducting three trials on each surface.  I circulate to ensure that groups are measuring accurately and everyone is participating.    Even after stressing the importance of measuring accurately, I still have to remind groups of what accurate looks like.  You can see in the video of group testing cardboard that I have to remind some groups to measure straight to the car.  They always want to measure in a straight line but if the car didn't travel in a straight line, they must measure how it traveled.  You can see in the video of group testing burlap that I also had to remind some groups to measure from the top of the ramp, not the side.

After being reminded of proper measuring techniques, groups began to get it right.  You can see in the video of group testing wood that this group measured correctly from the top of the ramp, to the back tires of the car.  They were careful to not move their finger when stretching the measuring tape and helped each other during the process.

## Wrap Up

10 minutes

Analyzing Data

After completing the experiment, I have groups create a bar graph to illustrate their results.  I allow students to work together in their groups to do this, but do require that each student has a completed graph drawn in his/her notebook.  I circulate while students work on their graphs to make sure they are completing them correctly.

After their graphs are completed, students use the data to write their conclusion.  I choose once graph from each group and display it under the overhead to share results with the other groups. All groups found that the carpet created the most friction.  It was not even close, the car stopped on the carpet within 20cm while it traveled over 150cm for all other ramps.  The majority of groups found that the cardboard had the least amount of friction so the car traveled the farthest on that surface.