Forces and Motion

Sarah Borenstein
Type Category
Instructional Materials
Student Guide , Lesson/Lesson Plan
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.



A teacher-submitted, NGSS-mindful lesson plan for using the PhET model "Forces and Motion - Basics". The model uses a tug-of-war with participants of different sizes and strengths, placed different distances from the center, in order to show how forces can combine in different ways to affect the motion of an object. The lesson itself includes a framing question, several investigations, and a request to back up a claim with evidence. NOTE: the web page given above is not itself the resource. The web page provides a link to a downloadable Microsoft Word document of the lesson plan, which is the resource.

Intended Audience

Educator and learner
Educational Level
  • Middle School
Access Restrictions

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

Performance Expectations

MS-PS2-2 Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.

Clarification Statement: Emphasis is on balanced (Newton’s First Law) and unbalanced forces in a system, qualitative comparisons of forces, mass and changes in motion (Newton’s Second Law), frame of reference, and specification of units.

Assessment Boundary: Assessment is limited to forces and changes in motion in one-dimension in an inertial reference frame and to change in one variable at a time. Assessment does not include the use of trigonometry.

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

Comments about Including the Performance Expectation
The lesson plan and student guide culminate with this very task, planning an investigation about how altering forces will change motion, then using the simulation to run the investigation. To address the part of the Performance Indicator involving the effect of mass on motion, the teacher could write an extension to the plan, and have students use the "Motion" section of the PhET simulation, which is about the effect of mass on motion.

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
This practice is mentioned by name in the lesson plan. Student tasks begin with finding a relationship between variables (force and distance) and motion. They then use a claim-evidence-reasoning argument model to answer the question “What causes objects to move or stay still?” The final task involves students asking an answerable question, then using the online simulation to run an investigation to collect evidence to answer it.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
Students make predictions, investigate using scaffolded experiments with the given simulations, and are asked to draw conclusions that directly relate to the relationship between the size of forces applied and the resulting change of motion.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
Students make predictions based on changes they will make to the model, then observe the effects of their changes, but the phrase “cause and effect” is not mentioned in the student handout. The teacher would need to guide students to the understanding that the independent variable (force from the "people") is the cause, and the dependent variable (motion) is the effect. This discussion might also be a good time/place to point out that the distance of people along the rope turned out to be a red herring (not a cause of change in motion), since the "people" in the simulation are directly attached to the cart by the rope no matter where they are physically standing. Students may also equate the different sizes of the "people" in the simulation with different masses, rather than different forces. Make sure to point out that the force arrows get labeled in Newtons, not kilograms. Relating the simulation to real scenarios may also be helpful here - have one student pull or push something hard and then pull or push the same thing gently, to show that the mass of the student is not directly related to the force he or she applies - the person's mass is not the cause of the motion.

Resource Quality

  • Alignment to the Dimensions of the NGSS: To fully integrate the crosscutting concept and the entirety of the Disciplinary Core Idea, the teacher will need to “fill in” a little bit to what is given in the student guide. The "filling in" includes a concept (relationship between mass and force) and some vocabulary (cause and effect). See the Teacher Tips above for recommendations.

  • Instructional Supports: The lesson scaffolds activities so as to build a knowledge base. The culminating task is open-ended. Modalities for student expression are limited to writing tasks. Students could perhaps be encouraged to draw a diagram to model the prediction they have for their final student-designed investigation, prior to testing it with the simulation, and accompany their results with another diagram that supports the evidence and/or reasoning section of their written response.

  • Monitoring Student Progress: The lesson does not include formal methods for monitoring student progress. Standard teacher techniques (circulating around the room checking in with students, whole-class or small-group discussions of some points, etc.) will work well as informal formative assessment. Students could also be asked to submit their “claim evidence reasoning (CER)” argument paragraph as a formal assessment, or these could be used to draft a more clear CER response in groups or as a whole class.

  • Quality of Technological Interactivity: The lesson plan and student guide downloaded easily. The simulation connected with this activity responds to student input, such that students can design and run their own experiments, within parameters. The purpose of the simulation is directly related to learning. The interface is intuitive and user-friendly. The simulation can be downloaded ahead of time to a computer or flash drive if internet connectivity is unreliable. The simulation uses Java. Another version of this simulation, with a slightly different layout, runs in HTML 5, which should run on tablets.