Change the net force
Hold mass fixed and observe how acceleration responds to different forces.
AP Physics 1 · Unit 2, Part 1 · Forces
Newton’s Second Law
Change net force and mass, compare acceleration, and use controlled trials to test Newton’s second law.
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Learn by doing
Three ideas you’ll put into motion
Change the mass
Keep the force fixed and compare the response of different masses.
Use the whole force model
Add opposing forces before predicting acceleration, then test your result.
The big idea
The key ideas, at a glance.
Acceleration follows net force
Use ΣF = ma. The direction of acceleration follows the net external force, which can differ from the direction of velocity.
Mass changes the response
At fixed net force, greater mass means smaller acceleration. Compare one changed variable at a time.
A quick comparison
Double the net force while keeping the mass the same.
The acceleration doubles.
Teaching this topic?Classroom fit, AP connections, and support
- Classroom fit
- Use for a concept introduction, guided independent practice, or a projected class discussion.
- Before students begin
- Free-body diagrams, signed force sums, and basic algebra.
- Built-in support
- Prepared scenes, guided prompts, and feedback on lesson questions.
- AP Physics 1 connections
- Unit 2: Newton’s second law, system mass, and force–acceleration relationships.
- Check for understanding
- Ask why the largest individual force does not always determine the acceleration.
- Optional extension
- Collect more data in the Newton’s Second Law lab.
Ready to test your thinking?
The first scene is set up. Start the lesson and explore.