This unit builds toward these performance expectations:

• HS-ETS1-3 Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics as well as possible social, cultural, and environmental impacts.
• HS-PS2-2 Use mathematical representations to support the claim that the total momentum of a system of objects is conserved when there is no net force on the system.
• HS-PS2-3 Apply scientific and engineering ideas to design, evaluate, and refine a device that minimizes the force on a macroscopic object during a collision.
• HS-PS2-1 Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration.

PS2.A: Forces and Motion

• Momentum is defined for a particular frame of reference; it is the mass times the velocity of the object. (HS-PS2-2)
• Newton’s second law accurately predicts changes in the motion of macroscopic objects. (HS-PS2-1)
• If a system interacts with objects outside itself, the total momentum of the system can change; however, any such change is balanced by changes in the momentum of objects outside the system. (HS-PS2-2),(HS-PS2-3)

ETS1.A: Defining and Delimiting Engineering Problems

• Humanity faces major global challenges today, such as the need for supplies of clean water and food or for energy sources that minimize pollution, which can be addressed through engineering. These global challenges also may have manifestations in local communities. (HS-ETS1-1)
• Criteria and constraints also include satisfying any requirements set by society, such as taking issues of risk mitigation into account, and they should be quantified to the extent possible and stated in such a way that one can tell if a given design meets them. (HS-ETS1-1, secondary to HS-PS2-3)

ETS1.B: Developing Possible Solutions

• When evaluating solutions, it is important to take into account a range of constraints, including cost, safety, reliability, and aesthetics, and to consider social, cultural, and environmental impacts. (HS-ETS1-3)
• Both physical models and computers can be used in various ways to aid in the engineering design process. Computers are useful for a variety of purposes, such as running simulations to test different ways of solving a problem or to see which one is most efficient or economical, and in making a persuasive presentation to a client about how a given design will meet his or her needs. (HS-ETS1-4)

ETS1.C: Optimizing the Design Solution

• Criteria may need to be broken down into simpler ones that can be approached systematically, and decisions about the priority of certain criteria over others (trade-offs) may be needed. (HS-ETS1-2, secondary to HS-PS2-3)

ETS2.B: Influence of Engineering, Technology, and Science on Society and the Natural World

• New technologies can have deep impacts on society and the environment, including some that were not anticipated. Analysis of costs and benefits is a critical aspect of decisions about technology.

Analyzing and Interpreting Data: This unit intentionally develops students’ engagement in this practice by providing the opportunity for students to analyze and interpret complex, real-world data using a variety of tools, technologies, and models, including simulations, video, algebra, force sensors, graphs, and data about policy and human behavior that can only be explained using science ideas.

• Analyze data using tools, technologies, and/or models (e.g., computational, mathematical) in order to make valid and reliable scientific claims or determine an optimal design solution.
• Evaluate the impact of new data on a working explanation and/or model of a proposed process or system.
• Analyze data to identify design features or characteristics of the components of a proposed process or system to optimize it relative to criteria for success.

Using mathematics and computational thinking: This unit intentionally develops students’ engagement in this practice. Throughout, students use algebraic thinking and graphical representations to interpret data patterns and derive mathematical models, including equations for the conservation of momentum and Newton’s second law to understand and explain the anchoring and investigative phenomena and weigh design solutions.

• Use mathematical, computational, and/or algorithmic representations of phenomena or design solutions to describe and/or support claims and/or explanations.
• Apply techniques of algebra and functions to represent and solve scientific and engineering problems.
• Use simple limit cases to test mathematical expressions, computer programs, algorithms, or simulations of a process or system to see if a model “makes sense” by comparing the outcomes with what is known about the real world.

Constructing Explanations and Designing Solutions: This unit intentionally develops students’ engagement in this practice. The unit includes several opportunities for students to construct explanations supported by multiple sources of evidence consistent with scientific ideas, principles, and theories. Throughout, students are also thinking about design solutions. They keep track of their explanations and design ideas in an Engineering Progress Tracker, and their culminating task is a Community Design Solution.

• Make a quantitative and/or qualitative claim regarding the relationship between dependent and independent variables.
• Apply scientific ideas, principles, and/or evidence to provide an explanation of phenomena and solve design problems, taking into account possible unanticipated effects.
• Design, evaluate, and/or refine a solution to a complex real-world problem, based on scientific knowledge, student-generated sources of evidence, prioritized criteria, and tradeoff considerations.

Engaging in Argument from Evidence: This unit intentionally develops students’ engagement in this practice. Students use an argumentation scaffold across Lessons 12-15 to deliberate about complex socio-ecological explanations and proposed solutions.

• Compare and evaluate competing arguments or design solutions in light of currently accepted explanations, new evidence, limitations (e.g., trade-offs), constraints, and ethical issues.

The following practices are also key to the sensemaking in this unit:

• Developing and Using Models
• Asking Questions and Defining Problems

Cause and Effect: This unit intentionally develops this crosscutting concept. Students reason about how vehicle designs affect safety. They see that systems are designed to cause specific effects and that decisions that we make can cause changes in our own communities.

• Empirical evidence is required to differentiate between cause and correlation and make claims about specific causes and effects.
• Cause and effect relationships can be suggested and predicted for complex natural and human designed systems by examining what is known about smaller-scale mechanisms within the system.
• Systems can be designed to cause a desired effect.
• Changes in systems may have various causes that may not have equal effects.

Scale, Proportion, and Quantity: This unit intentionally develops this crosscutting concept. Students use algebraic thinking to establish relationships between variables.

• The significance of a phenomenon is dependent on the scale, proportion, and quantity at which it occurs.
• Some systems can only be studied indirectly as they are too small, too large, too fast, or too slow to observe directly.
• Algebraic thinking is used to examine scientific data and predict the effect of a change in one variable on another (e.g., linear growth vs. exponential growth).

Patterns: This unit intentionally develops this crosscutting concept. The anchoring phenomenon is a set of complex data patterns that are not easy to explain and that we will return to across several lessons. Students continually use graphical representations of data to identify patterns in data.

• Patterns of performance of designed systems can be analyzed and interpreted to reengineer and improve the system.
• Mathematical representations are needed to identify some patterns.
• Empirical evidence is needed to identify patterns.

The following crosscutting concepts are also key to the sensemaking in this unit:

• Stability and Change of Systems
• Systems and System Models
• Structure and Function

Which elements of NOS are developed in the unit?

• Scientific Investigations Use a Variety of Methods. Scientific investigations use diverse methods and do not always use the same set of procedures to obtain data.
• Science Is a Human Endeavor. Science and engineering are influenced by society, and society is influenced by science and engineering.
• Science Addresses Questions about the Natural and Material World. Not all questions can be answered by science.
• Science Addresses Questions about the Natural and Material World. Science and technology may raise ethical issues for which science, by itself, does not provide answers and solutions.
• Science Addresses Questions about the Natural and Material World. Scientific knowledge indicates what can happen in natural systems–not what should happen. The latter involves ethics, values, and human decisions about the use of knowledge.
• Science Addresses Questions about the Natural and Material World. Many decisions are not made using science alone, but rely on social and cultural contexts to resolve issues.
• Science Models, Laws, Mechanisms, and Theories Explain Natural Phenomena. Laws are statements or descriptions of the relationships among observable phenomena.

This unit is anchored by a puzzling set of patterns in traffic collision data over time: while overall, vehicle fatalities have been decreasing steadily for decades, the trend appears to have stalled, and collisions and fatalities have been increasing. This phenomenon provides the context in which to investigate the physical relationships among mass, velocity, momentum, force, time, and acceleration, basic physical quantities that provide the foundation for the study of mechanics. Students will analyze statistics on vehicle collisions, analyze the motion of vehicles stopping to avoid collisions, and model vehicle collisions to understand how vehicles are designed to reduce the chances of injury in a collision by testing and evaluating designs that could change force interactions in the system. Lastly, the students compare and evaluate arguments on how we can make driving safer for everyone and develop their own design solutions in an engineering design challenge.

The vehicle collisions anchoring phenomenon was chosen from a group of phenomena aligned with the target performance expectations based on the results of a survey administered to almost 1,000 students from across the country and in consultation with external advisory panels that include teachers, subject matter experts, and state science administrators. This phenomenon includes a strong engineering component with a complex global problem and includes humans and human activity in the systems under study. The full physics course is designed to purposefully highlight a variety of different types of phenomena. While we design to privilege the interests of students to whom we owe an educational debt, we must not essentialize minority groups by assuming that a trend in the data equates to homogenous interests and experiences. Providing a diverse suite of entry points into content and practices creates more opportunities for every student to connect with the content.

The collisions phenomenon was chosen for the following reasons:

• Students showed high interest in explaining the puzzling data trends.
• To provide a diverse suite of entry points across the course, we were seeking an event that allowed students to consider a relevant societal problem.
• Teachers and administrators saw the phenomenon as interesting and on grade band.
• Explaining the mechanics of a collision using physics concepts grounds abstract ideas about momentum.
• Explaining the phenomenon addresses all the DCIs in the bundle at a high school level.
• Explaining the phenomenon requires the use of mathematical thinking at a high school level.
• In consultation with high school counselors, the team felt the phenomenon is relevant and important for high school students and could be approached from a trauma-informed perspective.

This unit is the third in the OpenSciEd High School Physics course sequence. It is designed to build on student ideas about forces and matter interactions from the second unit of the course. In the first unit of OpenSciEd HS Physics, students developed ideas around energy transfer and conservation in the context of charged particles (electrons) colliding with other electrons (electricity) to transfer energy across great distances. In the second unit of the course, the development of the concept of forces was needed in order to explain earth science phenomena that involve energy transfer across scales of time and space. In this unit, students develop a more-robust understanding of forces as vectors and use conservation of momentum and Newton’s second law to make predictions about the outcomes of collisions.

In the unit that follows this one, students will build on what they figured out about contact forces in previous units (tectonic plates rubbing, vehicles colliding) to understand gravity, a force that acts at a distance, and use what they figure out to explain the dynamics of orbiting objects. The fifth unit uses energy transfer, electromagnetism, wave mechanics, and forces at a distance to explain how food heats up in a microwave and if and how this technology might be dangerous for humans. In the final unit of the course, students will explore cosmology and the Big Bang, applying ideas about forces and energy from all five previous units on the largest scales.

The unit is organized into three lesson sets. Lesson Set 1 (Lessons 1-7) focuses on answering the question: What factors can make driving more risky? In the first lesson set, students develop models to show how distracted driving and changes in vehicle design might contribute to trends in vehicle safety over time. This leads them to wonder about distracted driving. They analyze video of two drivers encountering a sudden obstacle, one who is not distracted and one who is distracted, and plot each to show how being distracted affects the motion of the vehicle over time. They use mathematical models to generate data about how speed affects reaction distance and identify design features that can decrease reaction distances to prevent collisions in the event of a sudden obstacle. Then they use a hands-on investigation to develop a mathematical model for the time it takes a vehicle to come to a stop while braking. They define acceleration and rearrange their mathematical model into Newton’s second law. They then wonder what happens when avoiding a collision is not possible. They adapt their existing mathematical relationship to describe patterns between the masses and the changes in velocity of two colliding carts using videos, graphs, and simulations, co-developing a definition of momentum in the process. Finally, they put the pieces together in Lesson 7 and complete a transfer task that asks them to analyze and explain real data about bus safety.

Lesson Set 2 (Lessons 8-12) focuses on answering the question: How are vehicles designed to keep people safe? In the second lesson set, students analyze multiple design features of vehicles that are designed to keep people safe during collisions. They use simulation data to create a collision timeline for the crash test dummy in a vehicle cabin. They investigate how seat belts and airbags work together to stop a crash test dummy in a collision and make connections back to Newton’s second law. They then use simulation data to analyze how the design of vehicle crumple zones can also reduce forces on a crash test dummy and notice that the speed of the vehicle greatly impacts the outcome of a collision. In Lesson 12, students put the pieces together by creating a Gotta-Have-It Checklist for designing vehicle safety features and consider how design solutions might affect some people (or animals, plants) differently than others.

Lesson Set 3 (Lessons 13-15) focuses on answering the question: How can we make design decisions that will make driving safer for everyone? Students compare and evaluate vehicle safety design solutions and survey community members about local issues with transportation safety. In Lesson 14, students research an issue that is relevant to the community and develop and implement a plan for a Community Design Solution. Finally, they return to their DQBs in Lesson 15 and complete a transfer task that asks them to compare two vintage design solutions for catching pedestrians.

The following are example options to shorten or condense parts of the unit without eliminating important sensemaking:

• Lesson 4: Instead of conducting the Braking Lab, you could provide students with demonstrations and the sample data to do the analysis.
• Lesson 11: The Scientists Circle about M-E-F perspectives wraps up the crumple zone discussion but could be excluded or integrated into the Lesson 12 Gotta-Have-It Checklist discussion.

To extend or enhance the unit, consider the following:

• Lesson 3: Consider having students use the collision avoidance view of the Vehicle Collision Simulator to experiment with the relationships established.
• Lesson 6: If you have multiple smart carts, consider collecting the data shown in the videos in your classroom together. Be sure to test it out ahead of time, as it is easy for the measurements to be off because of error.
• Lesson 11: Have students collect the data using the simulation instead of providing them with the graph handouts.
• Lesson 14: Spend more time having students research and develop their community design solutions.
• All lessons: Remove scaffolds provided with science and engineering practices (SEPs) as a way to give students more independent work with the elements of these practices.

• Laura Zeller, Revision Unit Lead, BSCS Science Learning
• Zoë Buck Bracey, Field Test Unit Lead, BSCS Science Learning
• Whitney Mills, Field Test Unit Lead, BSCS Science Learning
• Michael Novak, Writer, Northwestern University
• Diego Rojas-Perilla, Writer, BSCS Science Learning
• Althea Hoard, Writer, Independent Consultant
• Joe Kremer, Writer, Denver Public Schools
• Caitlin Matyas, Writer, Independent Consultant
• Christopher Soldat, Writer, Independent Consultant
• Betty Stennett, Writer, BSCS Science Learning
• Alexis Gibson, Social Emotional Learning Consultant, Independent Consultant
• Inquirium, L.L.C., Collision Simulation Developer

• Madison Hammer, Production Manager, University of Colorado Boulder
• Erin Howe, Project Manager, University of Colorado Boulder
• Jamie Deutch Noll, Production Support, BSCS Science Learning
• Tyler Morris-Rains, Production Support, BSCS Science Learning
• Kate Herman, Copy Editor, Independent Consultant
• Stacey Luce, Copy Editor, BSCS Science Learning
• Chris Moraine, Media Production, BSCS Science Learning

An integral component of OpenSciEd’s development process is external validation of alignment to the Next Generation Science Standards by NextGenScience’s Science Peer Review Panel using the EQuIP Rubric for Science. We are proud that this unit has been identified as a quality example of a science unit. You can find additional information about the EQuIP rubric and the peer review process at the nextgenscience.org website.