In AP Physics 1, speed is a scalar quantity that measures how fast an object moves, calculated as distance traveled per unit time. Unlike velocity, speed has magnitude only and no direction, which is exactly the scalar-vs-vector distinction tested in Topic 1.1.
Speed is how fast something is moving, period. It's the rate at which an object covers distance, and because distance is a scalar, speed is a scalar too. The CED is explicit about this in Essential Knowledge under learning objective 1.1.A: distance and speed are scalar quantities, while position, displacement, velocity, and acceleration are vectors. That means speed gets a magnitude (like 5 m/s) but never a direction.
Here's the intuitive version. Speed is what your car's speedometer reads. It doesn't care whether you're heading north, south, or driving in circles. Velocity is the speedometer reading plus a compass. A car going around a track at a steady 30 m/s has constant speed but constantly changing velocity, because its direction keeps changing. That one sentence resolves about half the trick questions you'll see on this concept.
Speed lives in Topic 1.1 (Position, Velocity, and Acceleration) in Unit 1: Kinematics, and it directly supports learning objective 1.1.A, which asks you to describe quantities using magnitude and direction as appropriate. Speed is one of the CED's go-to examples of a quantity where direction is not appropriate. Getting speed vs velocity straight early matters because every later unit builds on velocity vectors, and the exam loves checking whether you know which one you're actually working with. Speed also reappears in Topic 10.2 (Periodic Waves), where wave speed describes how fast a pulse or wave pattern travels through a medium. Same scalar idea, totally different physical setting, which is exactly the kind of cross-unit connection AP Physics rewards.
Keep studying AP Physics 1 Unit 1
Velocity (Unit 1)
Velocity is speed with a direction attached. The magnitude of an object's velocity is its speed, but average speed (total distance over time) can differ from the magnitude of average velocity (displacement over time) whenever the path bends or doubles back.
Distance vs Displacement (Unit 1)
Speed and velocity inherit their scalar/vector status from these two. Speed comes from distance (scalar, path length), velocity comes from displacement (vector, straight-line change in position). If you can tell distance from displacement, the speed-velocity distinction is the same logic one step later.
Periodic Waves (Unit 10)
Wave speed tells you how fast a disturbance travels through a medium, and it depends on the medium, not on how hard you shake the source. The 2017 exam gave wave pulses moving 'with a speed of one unit per second' and asked you to predict where they'd overlap. That's literally just speed times time.
Free Fall (Unit 1)
In free fall, an object thrown upward returns to its launch height with the same speed it left with, but the opposite velocity. This is a classic spot where the exam tests whether you notice that speed is unchanged while velocity flipped sign.
Speed shows up two ways. First, as a conceptual trap in multiple choice. Questions describe circular or back-and-forth motion and ask whether speed, velocity, or both are constant, betting you'll forget that changing direction changes velocity but not speed. Second, as a given quantity in problem setups, like the 2017 short FRQ where two wave pulses travel toward each other at one unit per second and you have to figure out the string's shape at a later time. Other released FRQs, like the 2017 projectile-launch design question, hand you a launch speed and expect you to combine it with kinematics. Your job is almost never to define speed. It's to (1) classify it correctly as a scalar, (2) compute distance ÷ time or use it in v = d/t style reasoning, and (3) catch the moments when a question swaps 'speed' and 'velocity' on you.
Speed is a scalar (magnitude only); velocity is a vector (magnitude and direction). An object moving in a circle at constant speed has a changing velocity because its direction changes, which also means it's accelerating. Also, average speed uses total distance while average velocity uses displacement, so a round trip can have a high average speed but zero average velocity.
Speed is a scalar quantity, meaning it has magnitude only, and the CED lists it alongside distance as a classic scalar example under LO 1.1.A.
Average speed equals total distance divided by total time, while average velocity uses displacement, so they differ on any path that curves or reverses.
An object can have constant speed but changing velocity if its direction changes, like uniform circular motion, and that means it is accelerating.
In free fall, an object returns to its launch height with the same speed but opposite velocity, a distinction the exam tests often.
Wave speed in Topic 10.2 is the same scalar concept applied to a traveling pulse, and you can find a pulse's position with distance equals speed times time.
Speed is the scalar rate at which an object moves, calculated as distance traveled per unit time. It has a magnitude (like 12 m/s) but no direction, which is what separates it from velocity in Topic 1.1.
No. Speed is the magnitude part of velocity with the direction stripped off. A car circling a track at a steady 30 m/s has constant speed but changing velocity, because its direction keeps changing.
Yes. Acceleration is any change in velocity, and direction counts. An object in uniform circular motion keeps the same speed but accelerates the whole time because its velocity vector keeps turning.
Speed is a scalar. The AP Physics 1 CED explicitly names distance and speed as scalar quantities and position, displacement, velocity, and acceleration as vectors, so this exact classification is fair game on the exam.
Average speed is total distance over total time; average velocity is displacement over total time. On a round trip, your displacement is zero, so your average velocity is zero even though your average speed isn't.