Grade Level: Middle school
Time Required: 2 hours (wild guess!)
Subject Areas: Physical Science, Physics
Maker Challenge Recap
How does mass affect momentum in a head-on collision? Students explore this question and experience the open-ended engineering design process as if they are the next-generation engineers working on the next big safety feature for passenger vehicles. They are challenged to design or improve an existing passenger compartment design/feature so that it better withstands front-end collisions, protecting riders from injury and resulting in minimal vehicle structural damage. With a raw egg as the test passenger, teams use teacher-provided building materials to add their own safety features onto either a small-size wooden car kit or their own model cars created from scratch. They run the prototypes down ramps into walls, collecting distance and time data, slo-mo video of their crash tests, and damage observations. They make calculations and look for relationships between car mass, speed, momentum and the amount of crash damage. A guiding worksheet and pre/post-quiz are included.
- a few raw eggs (expect some to break during crash tests)
- model car base kits; such as a wooden car kit for $9 at https://www.teachersource.com/product/wooden-car-kit/energy, the engineering sail car class pack (enough for 30 students) for $48 at https://www.pitsco.com/Try-This-Engineering-Class-Pack, or individually for $2.25 at https://www.pitsco.com/try-this-engineering-kit; alternatively, provide assorted craft supplies from which students construct their own basic model car bases
- assorted building materials, such as cardboard, wooden craft sticks, tag board, foam sheets, felt sheets, cotton or polyester fill, chenille stems/pipe cleaners, plastic drinking straws, string/yarn, rubber bands, balloons
- assorted tools and adhesives, such as rulers, scissors, tape, white glue, hot glue
- wooden board for a ramp, 10-inches wide x 3-5-feet long, to run all model cars down for crash testing; alternatively, use sturdy cardboard
- plastic sheeting, to tape against the wall and floor for mess protection during testing
- washers and duct tape, to add equal weight to all cars, to improve the crash dynamics
- digital scale, to measure car mass
- smartphone or tablet, to video record the model cars in slow motion
- stopwatches, for timing crash tests
- (optional) Internet access for researching current car safety features
Worksheets and AttachmentsVisit [ ] to print or download.
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(Show students the 1:35-minute “Buckle Up PSA” YouTube video, which shows many slow-motion vehicle crash tests with dummies inside, provides accident statistics, and briefly recaps how vehicle safety features (car seats, boosters and seat belts) added over the years have saved lives; at https://goo.gl/JyJ6ws.
(Then introduce the design challenge—a hypothetical scenario in which students are the next-generation engineers challenged to come up with the next best design for a vehicle passenger compartment and/or safety features to keep the “passenger egg” safe during a front-end collision, with minimal vehicle damage.)
- Refer to the Engineering Design Process hub on TeachEngineering to guide your students through the challenge.
- About a week before starting the maker challenge, consider having students take the Speed & Momentum Pre/Post-Quiz. Review their answers to give you input for adjusting the challenge as needed. At activity end, administer the same quiz to assess learning gains.
- Have students use the Design Process Packet to guide them through the activity. This seven-page worksheet provides a place to record their research, ideas, sketches, plans, materials, data, calculations, analysis and conclusions.
- As necessary, with the class, briefly review the steps of the engineering design process and relevant vocabulary words—collision, momentum, speed, mass.
Research, Brainstorm, Plan and Prototype
- As a class, compile a list of safety features found on current vehicles. If students get stumped suggest a few examples to get the ideas flowing, such as roll cages, seat belts, booster seats, airbags, head rests or cushioned interior, upon which students can expand on and improve.
- Introduce the project constraints: To come up with a vehicle safety design feature for their small-size model cars that is not currently in use, or one that works better than those currently in use. A successful design is one that protects the “passenger egg” and is durable.
- Prompt students to use this information as a jumping off point to examine the provided building materials and note similarities, such as craft sticks being similar to metal framing bars, and foam/felt being similar to the insulation and padding incorporated into modern vehicles.
- If students work in partners or groups (best if no more than four per group), have them individually brainstorm and sketch a few ideas for what they want to build on top of the model car base, with the goal to update or come up with a new passenger compartment so the passenger survives a front-end crash with no injuries and minimal car damage.
- Teams decide on a design solution to prototype and test.
- Give teams plenty of time to build and do small rolling tests against a wall so they can see how the impact affects the materials.
- Teams document the materials they use and sketch their final designs.
- After all teams have created prototypes, use the digital scale to find the mass of each car. Having this information helps with the anecdotal conclusions about the mass and momentum of the cars.
Test and Analyze
- Students use stopwatches to time their crash test runs. Time from the moment of release to the moment of impact. Measure the ramp from the point of release to the wall, in meters. Record distance and time measurements. Tips: Using a smartphone or tablet to video record the testing runs in slow motion is helpful for both timing and analysis. For more reliable data, have students run multiple trials, 3-5, and average their findings. Doing this will, however, have an effect on the car, but also serves as a good indicator for durability.
- After testing, students record whether their test runs were successful—egg did not crack and car structure remained intact—or not.
- Students calculate how fast their cars went and the momentum of the vehicles. They examine the data for relationships.
- As a class, briefly discuss any relationships seen between the heavier cars and the amount of destruction from the crash and the calculated momentum. Consider graphing the data. Have students write down their conclusions based on the class data—how mass affects momentum and the consequences of a front-end collision.
Redesign and Rebuild
- Teams brainstorm ways to fix the issues they found with their passenger compartment designs. For example, they might decide to beef up the roll bars, add more padding or create areas intended to compact without affecting the egg.
- After students/teams finish their redesigns/rebuilds, they measure the mass of their redesigned cars and add it to the individual or class chart.
Test and Analyze
- Students re-measure the ramp length and test their redesigned prototypes. Again, they use stopwatches to measure the time from vehicle release to impact.
- Students add their new results data to the chart. As a class, discuss the overall relationships of mass, momentum and observational data about the egg and crash. If you asked students to graph their data, look at the graphs to visually compare mass and momentum.
- Students write down their revised/final conclusions about what they think the data shows.
How does mass affect momentum in a head-on collision? As needed, guide student thinking about the relationship between greater mass, greater momentum and resulting damage to the passenger compartment and possible egg injuries. Did the mass, momentum or speed consistently help to predict the outcome of injury to the passenger egg or the vehicle damage? Expect students to see some correlation between mass and the amount of damage done; the greater the mass, the greater the damage.
How is the engineering design process used in real life? As an example, car buyers who are parents might want more safety features than single people, but those features cost more, so engineers design a range of different designs that match the desires of different buyers. All products—including sneakers, airplanes, computers, phones, video games—are the result of engineering design. Engineers follow the same guiding steps and problem solving techniques in order to invent new designs and improve existing designs for products, structures and systems that help to improve our lives. People do not usually think about following the design process steps beyond solving engineering challenges—but that is what most of us regularly do when coming up with solutions! We research to find information and figure out possible solutions, then we move forward with the best solution, testing and improving it as we go.
If the wooden base car models are too light to result in much of a crash, add the same number of metal washers to the bottoms of all the cars; this additional mass results in better crashes without changing the relative comparisons.
Pay attention to the ramp angle in relationship to the wheel size and adjust the ramp angle as necessary so the cars don’t bottom out during the crash test runs.
- For lower grades, build based on what students know about vehicles and then redesign based on the problems that arise. Do the speed and momentum calculations as a class.
- For higher grades, do not provide model base cars. Instead, have teams design and build entire model cars from supplied materials.
- Have students graph their individual/class data to visually compare mass with momentum.
- Add a materials costs column to the DPP table so students can figure the cost of materials and compare overall cost efficiency of the vehicles.
- Compare static vs. elastic collisions by having students run cars down opposing ramps into one another.
- Study the change of force and acceleration by pushing the cars with different forces and/or sending cars down a longer ramp.
Copyright© 2017 by Regents of the University of Colorado; original © 2016 North Dakota State University
ContributorsBeth Patterson; Kulm School; Jace Duffield, NDSU
Supporting ProgramRET Program, College of Engineering, North Dakota State University Fargo
This curriculum was developed in the College of Engineering’s Research Experience for Teachers: Engineering in Precision Agriculture for Rural STEM Educators program supported by the National Science Foundation under grant no. EEC 1542370. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Last modified: January 19, 2021