Test static friction
Observe how friction adjusts while an object remains at rest.
AP Physics 1 · Unit 2, Part 1 · Forces
Static and Kinetic Friction
Increase a push, cross the slipping threshold, and compare how static and kinetic friction affect motion on surfaces and ramps.
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Learn by doing
Three ideas you’ll put into motion
Start sliding
Identify the threshold for slipping and compare the force during sliding.
Apply the model
Use the normal force and friction coefficients to explain motion on level surfaces and inclines.
The big idea
The key ideas, at a glance.
Static friction can adjust
Static friction satisfies fs ≤ μsN. The value μsN is its maximum, not its value in every situation.
Kinetic friction acts during sliding
In the simple model, fk = μkN. Its direction opposes relative sliding at the contact.
A quick comparison
A small push acts on a block that stays at rest on a level surface.
Static friction matches the push until its limit is reached.
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
- Normal force, force diagrams, and the distinction between rest and acceleration.
- Built-in support
- Prepared scenes, guided prompts, and feedback on lesson questions.
- AP Physics 1 connections
- Unit 2: static and kinetic friction and the normal force.
- Check for understanding
- Ask why using f = μN for every stationary object can give an incorrect force.
- Optional extension
- Compare trials in the Static Versus Kinetic Friction lab.
Ready to test your thinking?
The first scene is set up. Start the lesson and explore.