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# Hands-on ActivityCars: Engineering for Efficiency

(3 Ratings)

### Quick Look

Time Required: 2 hours 30 minutes

(three 50-minute class periods)

Expendable Cost/Group: US \$1.00

Group Size: 2

Activity Dependency: None

Subject Areas: Science and Technology

NGSS Performance Expectations:

 3-5-ETS1-1 3-5-ETS1-2

### Summary

Students learn how the aerodynamics and rolling resistance of a car affect its energy efficiency through designing and constructing model cars out of simple materials. As the little cars are raced down a tilted track (powered by gravity) and propelled off a ramp, students come to understand the need to maximize the energy efficiency of their cars. The most energy-efficient cars roll down the track the fastest and the most aerodynamic cars jump the farthest. Students also work with variables and plot how a car's speed changes with the track angle.
This engineering curriculum aligns to Next Generation Science Standards (NGSS).

### Engineering Connection

The energy use and pollution associated with transportation is one of the largest issues facing society today. By building energy-efficient cars, engineers can lower the negative impacts that cars have on the environment and ultimately help improve our lives. The energy efficiency of a car is affected by a variety of factors, including size, aerodynamics, weight, and the rolling resistance of the wheels. Engineers must know all about these factors to design better cars.

### Learning Objectives

After this activity, students should be able to:

• Describe the characteristics that affect a car's energy efficiency.
• Explain how rolling resistance affects a car's energy efficiency.
• Describe how a car's shape and size are related to aerodynamics.
• Explain the steps of the engineering design process.
• Explain the difference between an independent and dependent variable.
• Plot the results of a simple experiment on a graph.

### Educational Standards Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards. All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org). In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

###### NGSS: Next Generation Science Standards - Science
NGSS Performance Expectation

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. (Grades 3 - 5)

Do you agree with this alignment?

Click to view other curriculum aligned to this Performance Expectation
This activity focuses on the following Three Dimensional Learning aspects of NGSS:
Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
Define a simple design problem that can be solved through the development of an object, tool, process, or system and includes several criteria for success and constraints on materials, time, or cost.

Alignment agreement:

Possible solutions to a problem are limited by available materials and resources (constraints). The success of a designed solution is determined by considering the desired features of a solution (criteria). Different proposals for solutions can be compared on the basis of how well each one meets the specified criteria for success or how well each takes the constraints into account.

Alignment agreement:

People's needs and wants change over time, as do their demands for new and improved technologies.

Alignment agreement:

NGSS Performance Expectation

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. (Grades 3 - 5)

Do you agree with this alignment?

Click to view other curriculum aligned to this Performance Expectation
This activity focuses on the following Three Dimensional Learning aspects of NGSS:
Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
Generate and compare multiple solutions to a problem based on how well they meet the criteria and constraints of the design problem.

Alignment agreement:

Research on a problem should be carried out before beginning to design a solution. Testing a solution involves investigating how well it performs under a range of likely conditions.

Alignment agreement:

At whatever stage, communicating with peers about proposed solutions is an important part of the design process, and shared ideas can lead to improved designs.

Alignment agreement:

Engineers improve existing technologies or develop new ones to increase their benefits, to decrease known risks, and to meet societal demands.

Alignment agreement:

###### Common Core State Standards - Math
• Reason abstractly and quantitatively. (Grades K - 12) More Details

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• Multiply and divide within 100. (Grade 3) More Details

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• Represent and interpret data. (Grade 4) More Details

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• Represent real world and mathematical problems by graphing points in the first quadrant of the coordinate plane, and interpret coordinate values of points in the context of the situation. (Grade 5) More Details

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• Fluently multiply multi-digit whole numbers using the standard algorithm. (Grade 5) More Details

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###### International Technology and Engineering Educators Association - Technology
• Students will develop an understanding of the attributes of design. (Grades K - 12) More Details

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• Students will develop an understanding of engineering design. (Grades K - 12) More Details

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• Apply the technology and engineering design process. (Grades 3 - 5) More Details

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• Evaluate designs based on criteria, constraints, and standards. (Grades 3 - 5) More Details

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###### State Standards
• Multiply and divide within 100. (Grade 3) More Details

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• Represent and interpret data. (Grade 3) More Details

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• Appropriate measurement tools, units, and systems are used to measure different attributes of objects and time. (Grade 4) More Details

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• Graph points on the coordinate plane to solve real-world and mathematical problems. (Grade 5) More Details

Do you agree with this alignment?

• Represent real world and mathematical problems by graphing points in the first quadrant of the coordinate plane, and interpret coordinate values of points in the context of the situation. (Grade 5) More Details

Do you agree with this alignment?

• Fluently multiply multi-digit whole numbers using standard algorithms. (Grade 5) More Details

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Suggest an alignment not listed above

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### Materials List

Each group needs:

• 5 Popsicle® / hobby sticks
• 4 Lifesavers® mint candies (Tip: Use the mint-flavored candies because they do not get as sticky as the fruit-flavored ones.)
• 3 drinking straws (small enough diameter to fit inside the mint candy holes)
• 3 index cards
• Car Design Worksheet, one per student

To share with the entire class:

• scissors
• play money (Monopoly® money works well)
• rain gutter section(s), ~7 ft in length
• duct tape (or other heavy duty tape)
• cardboard ramp
• electric fan
• projector, for showing the attached PowerPoint presentations
• stopwatch (if racing only one car at a time)

### More Curriculum Like This

Upper Elementary Lesson
Form vs. Function

Students take a closer look at cars and learn about some characteristics that affect their energy efficiency, including rolling resistance and the aerodynamics of shape and size. They come to see how vehicles are one example of a product in which engineers are making changes and improvements to gain...

High School Lesson
A Tale of Friction

High school students learn how engineers mathematically design roller coaster paths using the approach that a curved path can be approximated by a sequence of many short inclines. They apply basic calculus and the work-energy theorem for non-conservative forces to quantify the friction along a curve...

### Pre-Req Knowledge

Some graphing skills.

### Introduction/Motivation

How far can a car travel on one gallon of gas? (Answer: It depends on the car, but usually between 6 and 70 miles.) Do you think all cars are the same? (Answer: No) How about a semi-truck? (Answer: Definitely not.) What makes the difference in a vehicle's energy efficiency? A car's energy efficiency depends on many things, including its weight, its rolling resistance, and its aerodynamics. A car that is energy efficient can travel farther on the same amount of gas, which saves the driver money. Creating more energy-efficient cars also decreases air pollution and helps decrease greenhouse gas emissions due to automobile emissions. Also, gasoline is made from oil, a fossil fuel. Oil is a non-renewable energy source, which means that when it is used up, no more is available. For these reasons, engineers are continually figuring out ways to make cars more energy efficient by decreasing their air resistance, rolling resistance, and weight.

The aerodynamics of a car is dependent on how much air the car has to move out of the way as it travels along a road. Engineers often design cars to resemble aerodynamic animals and shapes in nature. Can you think of any aerodynamic animals? (Possible answers: Fish, birds, sharks.) These animals move through the air (or water) easily and use little energy because they are sleek in their shapes, having no sharp corners or flat surfaces facing the wind. This causes the air to flow smoothly (efficiently) over them. A sleek car moves more easily through the air than a semi-truck does, which means the car is more energy efficient.

The amount of energy a car uses can also be affected by the resistance of a car's tires on the road surface. You need to be able to find the balance between the amount of resistance, or friction, needed to keep the vehicle on the road and the ability to move efficiently without it flying off the road or being "stuck" to the road. Engineers design tires that increase a car's energy efficiency by rolling smoothly while making sure they are "sticky" enough to stay safely on the road, especially through corners and on wet surfaces. A great example of this would be a NASCAR race. Have any of you watched racing on television? The tires they use are expertly engineered so that the cars can reach high speeds while staying on the track during the tight corners.

Finally, a car's weight affects its energy efficiency. Is it harder to push a loaded grocery cart or an empty one? (Answer: Loaded) How about if you had to push the grocery cart uphill? Would you rather do it empty or full? (Answer: Empty) A car's weight determines how much energy it takes to accelerate, or speed up, the car, and it also affects how much energy it takes to move the car up a hill. Heavier cars are less energy efficient than lighter ones. Engineers use newly created, innovative materials whenever possible to reduce the weight of cars, as well as find ways to build them smaller so fewer materials are needed, which in turn reduces the weight of the car.

All of these factors contribute to a car's energy efficiency, with some of them being more important at high speeds and others being more important at low speeds.

All of these factors are considered variables, or something that you can change in an experiment or test. Engineers perform experiments on the many different variables to design cars for different purposes. When engineers perform experiments, they test only one variable at a time, while making sure that all of the other potential variables are kept unchanged. A variable that is kept from changing during an experiment is called a control. At the end of this activity, we will conduct several experiments to see how changing the angle of the track affects the speed of a car. In this case, the angle of the track is called the independent variable because we intentionally change it to gauge its affect on our vehicles. The speed of the car is called the dependent variable because it will be affected by the changes we make to the angle of the track. Once we have chosen our variables, we need to be very careful to control all other factors so that we get really accurate results. Let's get started!

### Procedure

Before the Activity

• Decide which of two ways to set up the activity: To run the activity as a series of two cars competing against each other (that is, two separate cars being raced at once), set up two rain gutter race tracks at approximately a 30-degree angle from the ground (see Figure 1). Tape the two gutters together to ensure the tracks are even. To run the activity with only one car racing at a time, use a single track and a stopwatch to record individual race times.
• Gather materials and make copies of the Car Design Worksheet.
• On Days 1 and 3, have the attached PowerPoint presentations ready to show.
• Set up race brackets, depending on number of student groups.

With the Students

Day 1 (or first hour)

1. Show the Day 1 PowerPoint presentation, as part of the Introduction/Motivation.
2. Divide the class into groups of two or three students each.
3. Hand out the worksheets.
4. Give \$700 of play money to each group.
5. Have students follow the steps in the worksheet (look at constraints, brainstorm ideas, draw a design, determine cost, re-design if over budget).
6. Once groups have completed detailed designs that are within budget, have them purchase materials. Encourage them to reserve some funds to make later modifications (improvements) to their original designs.
7. Have groups begin assembling their model cars.

Day 2 (or second hour)

1. Briefly remind students of the activity goals.
2. Have groups work on completing the assembly of their model cars.
3. Have students test cars and make changes to improve the designs.
4. Once all students have completed their model cars and made improvements, collect all of the cars at the front of the classroom.
5. Race cars against each other using double elimination to find the most energy efficient car (that is, cars are raced twice; after each race, the winner moves on to the next round; if a car is deemed the "slowest" car in more than two races, it is eliminated from the trials). If a single track is being used, record times and eliminated the slowest cars after two runs down the track. Have students record on their worksheets the fastest time for each car.
6. As a class, discuss why the winning car was the most energy efficient by examining its aerodynamics, rolling resistance, and size.
7. If time allows, place a ramp about 6 inches away from the bottom of the rain gutters, as shown in Figure 2. If available, place a fan flat on the ground blowing air upwards. Have students run their model cars down the gutters and jump them off the ramp. Mark where each car lands.
8. Discuss why specific cars jumped well and others did not.

Day 3 (or third hour)

1. Using the Day 3 PowerPoint Presentation, introduce the topic of variables.
2. Select the fastest car from the previous day's races to use to collect data.
3. Race the cars at the track angles specified in the worksheet, and have students record the times.
4. Have students practice graphing by having volunteers graph each data point on a graph drawn (or projected) on the board.
5. Discuss the shape of the graph with the students.
6. Have students predict the speed of the car at an angle that is less than 10 degrees and at an angle greater than 60 degrees. Record predictions.
7. Test students' predictions by moving the track to the specified angle and timing the car.

### Vocabulary/Definitions

aerodynamics: The ability of an object to cut through air (or water) efficiently

control: A variable that you are careful to keep the same during an experiment.

dependent variable: A variable that changes in value when you change an independent variable. Usually this is the variable about which you collect data during an experiment.

energy efficiency: Being able to do more with less energy.

independent variable: A variable you intentionally change in an experiment. Usually, the intent of the experiment is to see how a change in this variable affects the dependent variable.

rolling resistance: The force of friction acting on a rolling object by the ground to slow it down.

variable: Something that can be changed in an experiment.

### Assessment

Pre-Activity Assessment

Class Discussion: As a class, discuss the definitions of energy efficiency and aerodynamics. Have groups come up with three different factors they think will affect the energy efficiency or aerodynamics of their model cars. Write these factors on the board for all students to refer to during the design phase.

Activity Embedded Assessment

Car Design Worksheet: Have students follow the steps on the worksheet. Check the groups at each step and make sure they have adequately completed the associated task. For instance, the final design should include several different viewpoints and be adequately labeled.

Post-Activity Assessment

Graphing Exercise: As a class, graph the results of the experiment together. Have volunteers graph individual points on the board while students complete the graphs on their worksheets. Discuss the shape of the graph and its meaning. See the sample worksheet for information on typical values.

Activity Extensions

Perform a second experiment, this time using the weight of the model cars as the variable. Record the speed of a car with different amounts of weight attached, and graph the data. Compare the data from the different experiments. Which variable had the greatest effect on the car's speed? How do the two graphs compare? Are they different or the same?

### Investigating Questions

What characteristics do the fast cars have in common?

What is the most important characteristic that made the cars go fast?

What effect does changing the angle of the track have on the car speed?

### Safety Issues

Watch that students use care when using scissors.

### Troubleshooting Tips

If students have trouble designing cars with rolling wheels, suggest that one way to do this is to use the the drinking straws as axles and the mint candies as wheels.

Make sure the fan is slightly elevated from the floor to create a good air flow.

### Contributors

Eszter Horanyi, Jake Crosby, William Surles, Janet Yowell

### Supporting Program

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

### Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education, and National Science Foundation GK-12 grant no 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.