Everything you need to master Unit 1 — scalars vs. vectors, position, velocity, acceleration, motion graphs, reference frames, and projectile motion. The foundation for every other unit in AP Physics 1.
10–15% of the AP exam
7 study resources
College Board aligned
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Seven free resources for Unit 1 — pick the one that fits how you learn.
Unit 1 covers Kinematics — the study of motion without worrying about what causes it. This is where physics starts: learning to describe HOW objects move using position, velocity, and acceleration. You'll also master the difference between scalars (numbers with just size) and vectors (numbers with size AND direction), which is foundational for every other unit.
The College Board organizes Unit 1 into 5 topics: (1.1) Scalars and Vectors in One Dimension, (1.2) Displacement, Velocity, and Acceleration, (1.3) Representing Motion with graphs and the three kinematic equations, (1.4) Reference Frames and Relative Motion, and (1.5) Vectors and Motion in Two Dimensions (including projectile motion).
Unit 1 makes up roughly 10–15% of the AP Physics 1 exam. It's a moderate weight, but everything in Unit 2 (Forces) builds directly on the kinematic ideas here — so don't skip it, even if you've seen this material in Honors Physics.
Key terms preview
A taste of what you'll find in The Essentials and Flashcards.
Scalar vs. Vector
Scalars have magnitude only (speed, distance); vectors have both magnitude and direction (velocity, displacement, acceleration).
Displacement
The straight-line change in position from start to finish, with direction. A vector — not the same as distance.
Acceleration
The rate of change of velocity. An object accelerates when its speed OR its direction changes.
Kinematic Equations
The "Big Three" equations for constant acceleration that connect position, velocity, acceleration, and time.
Reference Frame
The viewpoint from which motion is measured. Different observers may measure different velocities, but they agree on acceleration.
Projectile Motion
2D motion where horizontal velocity is constant and vertical motion is free fall — handled as two independent 1D problems.
1. Motion is described by position, velocity, and acceleration — and they're linked through time
Velocity tells you how fast position is changing. Acceleration tells you how fast velocity is changing. These three quantities are the entire vocabulary of motion. Master the connections between them — slopes on graphs, areas under curves, and the kinematic equations.
2. Direction matters — vectors are different from scalars
Distance and speed don't care about direction. Displacement, velocity, and acceleration do. Mixing these up is the most common Unit 1 mistake. A car driving in a circle at constant speed is STILL accelerating because its direction is changing.
3. Two-dimensional motion is really just two one-dimensional problems
In 2D, the horizontal and vertical motions are independent. Projectile motion has zero acceleration horizontally but constant downward acceleration (g) vertically. Solve each direction separately, then combine. Time is the only thing they share.