College Board-Aligned Original Notes

AP Physics 1: Algebra-Based Unit 2 Topic 7: Kinetic and static friction

Connect Kinetic and static friction to a model, the evidence that supports it, and the variables that change the system.

Unit 2: Force and Translational Dynamics. College Board exam weighting listed for this unit: 18%-23% of multiple-choice exam score.

What to Know

Identify the system, surroundings, and scale before explaining a process.
Use diagrams, graphs, and tables as evidence rather than decoration.
For quantitative questions, keep units visible from the setup through the final answer.
Always connect this topic back to the larger unit: Force and Translational Dynamics.

Detailed Notes

Kinetic and static friction belongs to Force and Translational Dynamics, so study it as part of a larger scientific system rather than as a stand-alone fact. Start by identifying what is being described, what is changing, and what evidence would let you defend a claim.

In AP Physics 1: Algebra-Based, strong answers usually connect a visible pattern to an underlying mechanism. That means explaining not only what happens, but why it happens at the particle, organism, environmental, or system level.

For AP-style questions, expect this topic to appear with graphs, diagrams, data tables, experiments, or written scenarios. Your job is to describe the evidence, apply the correct concept, and explain the reasoning that connects them.

Key Vocabulary

Force

An interaction that can change an object's motion.

Free-body diagram

A diagram showing all external forces acting on an object.

Net force

The vector sum of all forces on an object.

Friction

A contact force that opposes relative motion or attempted motion.

Quick Practice

How would you explain Kinetic and static friction in one or two AP-style sentences?

Name the concept, apply it to a specific example or source, and explain the reasoning that connects the evidence to your answer.