Authentic Lessons for 21st Century Learning

Go, Car, Go

Newton's 2nd Law of Motion

K20 Center, Alexandra Parsons | Published: September 23rd, 2025 by K20 Center

  • Grade Level Grade Level 9th
  • Subject Subject Science
  • Course Course Physical Science, Physics
  • Time Frame Time Frame 3-4 class period(s)
  • Duration More 145 minutes

Summary

This lesson is an investigation of the relationship between force, mass, and acceleration (F=ma). The lesson includes a lab activity, research poster, and reflection to introduce and reinforce Newton's 2nd Law of Motion.

Essential Question(s)

How do mass and speed affect one another?

Snapshot

Engage

Students will watch a video about a child lifting a car and connect it to Newton’s Second Law through the Preflections strategy.

Explore

Students will conduct an experiment to investigate how force and mass affect the acceleration of a cart.

Explain

Students will create a research poster to communicate their investigation, data, and conclusions.

Extend

Students will use a CER framework to justify why F=ma explains their experimental results.

Evaluate

Students will design and solve real-world problems that apply Newton’s Second Law.

Materials

  • Lesson Slides (attached)

  • Guided Inquiry Hanging Mass Lab handout (attached; one per student)

  • Open Inquiry Hanging Mass Lab handout (attached; optional; one per student)

  • Data Tables and Graph handout (attached; one per student)

  • Claim-Evidence-Reasoning handout (attached; one per student)

  • Create the Problem handout (attached; one per student)

  • Projector and speakers

  • Physic Carts or cars

  • Pully + Clamp

  • String (non-stretchy)

  • Hanging masses (suggested: 25 g, 50 g, 75 g, 100 g, 125 g)

  • Meter sticks or tape measure

  • Balance scales 

  • Timers or stop watches

  • Tape

  • Safety goggles

  • Lab handouts, one for each student

  • Sticky easel pad paper

  • Markers (Mr. Sketch, Sharpie, etc.)

Engage

10 Minute(s)

Use slides 1-4 to introduce the topic, objectives, and essential question to the extent that you feel necessary. Display slide 5 and play the “Hero Kid Lifts Car Off Dad” YouTube video. Instruct students to pay attention to how mass and force influence motion and to notice connections to real-world examples they are already familiar with. After the video, move to slide 6 and introduce the Preflections strategy. Explain that students will write down their initial thoughts about what they expect to learn in the lab. Provide the prompt: How does this video relate to Newton’s Second Law? Allow two minutes of quiet writing time for students to record their responses, then collect the Preflection responses to be revisited after the lab.

Explore

45 Minute(s)

Assign students to work in groups of 2–4, using the provided lab materials to investigate how the net force on a cart affects its acceleration. Give each student a copy of either the Guided Inquiry Hanging Mass Lab or the Open Inquiry Hanging Mass Lab, depending on the level of independence appropriate for the group. Explain that in the Guided Inquiry version (explained on slides 7-8), they are to follow structured steps to collect and analyze data, while in the Open Inquiry version (explained on slides 9-10), they will design and carry out the experiment themselves, making decisions about what to test, how to measure, and how to record their data. Emphasize that this is an opportunity to apply critical thinking and problem-solving skills, to observe patterns in data, and to explore the relationship between force, mass, and acceleration. Remind students to collaborate, make careful measurements, and take thorough notes because the quality of their observations and analysis will support their later reflections and lab report.

Explain

45 Minute(s)

After groups have completed their lab conclusions, use the Research Poster instructional strategy to enable the students to showcase their findings. Display slide 18 and explain that the information included on the poster should reflect the different sections of the lab report they completed during the lab (Title, Goal, Hypothesis, Procedure, Data Tables, Graph, Analysis, and Conclusion) so that the poster is a clear and accurate summary of their investigation.

Provide students with guidelines about how to create an effective poster. For students who need additional assistance, direct them to https://guides.nyu.edu/posters. This is a resource that outlines what to include and provides assistance with how to lay it out. Emphasize to students the importance of clarity, readability, and visual organization. These qualities will make the findings easy to understand. 

Once the posters have been completed, display them around the room. Move to slide 19 and have each group share their main findings and conclusions. While students are presenting their findings, actively observe their understanding, identify misconceptions, and intervene as needed to clarify results or guide discussions. 

Extend

30 Minute(s)

Pass out the Claim-Evidence-Reasoning handout. Display slide 20. Have students frame their explanation as a CER (Claim, Evidence, Reasoning) response. Their claim should state that Newton’s Second Law accurately describes the relationship between force, mass, and acceleration. Their evidence should draw directly from their lab data, comparing measured accelerations with the net force applied (from the hanging mass) and showing how changes in the system mass affected results. Their reasoning should connect these patterns to the physics principle: the net force on an object is what causes its acceleration, scaled by its mass.

Encourage them to:

  • Use their graphs to support that acceleration is proportional to force when mass is constant and inversely proportional to mass when force is constant.

  • Explicitly connect “the data shows this” to “the data shows this because Newton’s Second Law predicts it.”

Evaluate

15 Minute(s)

Pass out the Create the Problem handout. Display slide 21. Using the Create the Problem strategy, explain to students that they will design their own real-world problem based on a given solution, such as “F = 6 N.” They should include the object’s mass, acceleration (or force), and a realistic context like a cart, bike, or ball. Display slide 22 and ask students to solve their own problem to ensure it works and provide an explanation of how their problem demonstrates Newton’s Second Law.

Next, display slide 23 and have students trade problems with a partner and solve each other’s scenario. At the end of the activity, instruct students to turn in their problems, solutions, and justifications for the teacher to review.

Resources