Crashes and Collisions

Betterlesson Ryan Keser
Type Category
Instructional Materials
Lesson/Lesson Plan , Experiment/Lab Activity , Interactive Simulation
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



Students explore the motion of objects after collisions. The objects have a range of masses and shapes.  The concept of conservation of momentum is explored.  Students extend the learning with an online simulation of collisions.  Emphasis is on finding and identifying patterns, and on using them to construct explanations for events.  It is recommended that students already have an understanding of forces and of Newton’s Laws of Motion, as this lesson confines itself to collisions and momentum.

Intended Audience

Educator and learner
Educational Level
  • Middle School
  • Grade 8
  • Grade 7
  • Grade 6
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

MS-PS2-1 Apply Newton’s Third Law to design a solution to a problem involving the motion of two colliding objects.

Clarification Statement: Examples of practical problems could include the impact of collisions between two cars, between a car and stationary objects, and between a meteor and a space vehicle.

Assessment Boundary: Assessment is limited to vertical or horizontal interactions in one dimension.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
This lesson is designed to give students experience with the behavior of pairs of colliding objects. It is intended to allow students to construct explanations about how the objects will behave, so it is meant to be an introduction to collisions, rather than an assessment. The emphasis is on discovering momentum, rather than on measuring forces, so the connection between collisions and Newton’s Third Law would be a logical “next step” lesson in working toward this Performance Expectation.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Students are specifically asked to use their data and observations, to explain how the relationship between masses in a collision affects the result of the collision. The relationship between the masses is quantitative. The relationship between resulting velocities is qualitative, and includes a talking point about friction and how its effects mean that quantitative velocities may not be significant. Students also use a simulation in which both the masses and the velocities are quantitative, and friction is not in play. The lesson culminates with students creating an explanation of the law of conservation of momentum, based on their experiences and a reading, and then relating their explanation back to situations described as a warmup at the beginning of the lesson. The lesson writer includes a short video clip for teachers, sharing ideas to extend the lesson and incorporate another bullet point of this practice, “Apply scientific ideas, principles, and/or evidence to construct, revise and/or use an explanation for real-world phenomena, examples, or events.”

Disciplinary Core Ideas

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
Again, the word “forces” does not appear in the lesson. A teacher could help students to quickly see a similarity between momentum (mass x velocity) and force (mass x acceleration). For more advanced middle school students, this could lead to a discussion of how Newton created the 2nd Law through the lens of momentum (F = change in momentum / change in time) which we now simplify to F = ma.

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
The lesson does not overtly use the word “force”. The lesson is meant as an introduction to collisions, so its focus is on momentum. It is recommended that students already have an understanding of forces, and of Newton’s Laws of Motion, so that a teacher could easily remind students that the changes in motion they see are caused by force pairs.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
Students are specifically asked to find patterns in their chart data, and to connect those patterns to the results of their collisions. A teacher could also connect to another detail, “Patterns can be used to identify cause-and-effect relationships”, by overtly referring to the motion of masses before the collision as a “cause” and after the collision as an “effect”, during the portion of the lesson where students explain why the objects moved as they did.

Resource Quality

  • Alignment to the Dimensions of the NGSS: The lesson uses both hands-on phenomena and simulations to help students construct an explanation for how collisions work. The cross-cutting concept of Patterns is overt in the lesson, and central to students’ completion of the culminating task. Although the concept of the lesson is central to eventual achievement of the Performance Expectation, the core ideas involving forces are only tangentially represented, so it is recommended that students already have some familiarity with the concept of forces, and with Newton’s Laws of Motion.

  • Instructional Supports: The lesson begins with relatable scenarios, then has students use phenomena to construct their own understanding of the conservation of momentum. Students express their ideas in written form in their science journals, and share their ideas orally or with individual whiteboards. Ideas for differentiation are not included; a teacher could have students create their own chart, use the chart provided, or be given a clearer and more specific chart. Sentence frames for the writing prompts would be helpful for students who struggle to explain their thoughts in writing, or for whom the questions as written are too broad.

  • Monitoring Student Progress: The lesson does not include a summative assessment, nor are rubrics, scoring guides or keys provided for the student work. Since the lesson is best suited as part of a progression, rather than a culmination, these lacks are not a serious issue. Several opportunities are embedded for formative assessment, particularly of students’ understanding of patterns and of their ability to create an explanation from data.

  • Quality of Technological Interactivity: The PhET interactive included in the lesson is sturdy, robust and responsive. It uses Flash, which may be an issue on some computers and tablets. The simulation uses spheres of various masses, rather than “real world” objects, which can minimize variables, but also may be of less interest to students than actual objects.