In AP Calculus, displacement is the net change in an object's position over a time interval, computed as the definite integral of velocity, ∫v(t)dt from a to b. Unlike total distance traveled, displacement can be negative because it counts direction.
Displacement is the net change in position. If a particle starts at one spot and ends at another, displacement tells you how far the ending point is from the starting point, and in which direction. In calculus terms, displacement from t = a to t = b is the definite integral of velocity: ∫ₐᵇ v(t) dt.
This is the accumulation idea from the CED in action. Velocity is the rate of change of position, so integrating that rate over an interval gives you the net change in position (that's the essential knowledge behind LO 8.3.A). The word "net" is doing heavy lifting here. If the particle moves right 10 units and then left 4, the displacement is +6, not 14. Negative velocity subtracts from the integral, so any backward motion partially cancels forward motion. Picture walking three blocks east, then three blocks west. You walked six blocks, but your displacement is zero because you ended up where you started.
Displacement lives in Unit 8 (Applications of Integration), specifically Topic 8.3, where LOs 8.3.A and 8.3.B ask you to interpret a definite integral as net change and apply it in context. It's the cleanest example of the entire accumulation theme. The definite integral of a rate of change equals the net change of the quantity, and "integrate velocity to get displacement" is that sentence in motion form.
For BC, displacement comes back in Unit 9 (Topic 9.5), where you integrate vector-valued or parametric velocity functions component by component (LO 9.5.A), and it pairs with Topic 8.13, where distance traveled along a curve uses arc length. Particle motion shows up on the exam almost every year, so knowing exactly what displacement means (and what it doesn't) is non-negotiable.
Keep studying AP Calculus Unit 8
Visual cheatsheet
view galleryTotal Distance Traveled (Unit 8)
Distance traveled is ∫|v(t)|dt, the integral of speed. Taking the absolute value stops backward motion from canceling forward motion. Displacement and distance are equal only when the velocity never changes sign on the interval.
Velocity (Units 4 and 8)
Velocity is the derivative of position, so integrating it undoes that derivative and recovers the change in position. Displacement is literally the Fundamental Theorem of Calculus applied to motion.
Position Function (Unit 8)
Displacement is a change in position, not the position itself. To find where the particle actually is, you need an initial condition. The 2018 FRQ gave x(0) = −5 exactly so you'd compute x(t) = −5 + ∫₀ᵗ v(s)ds. Position equals starting point plus displacement.
Integrating Vector-Valued Functions (Unit 9, BC only)
In BC, a particle moving in the plane has a velocity vector, and you integrate each component separately to get the displacement in x and y. Same accumulation idea, just done twice.
Particle motion is one of the most reliable FRQ setups in AP Calculus. The 2018 FRQ Q2 and 2024 FRQ Q2 both gave a velocity function for a particle on the x-axis and asked you to work with position, displacement, and distance. The classic moves you need are: (1) compute displacement as ∫v(t)dt, usually with a calculator since these appear in the calculator section, (2) find position by adding displacement to an initial position, and (3) find total distance by integrating |v(t)|.
Multiple-choice stems look like the practice versions of this: "the velocity of an object is v(t) = t² − t; find the displacement from t = 1 to t = 3." That's a straight definite integral, no absolute value. The trap answer is always the total distance value, or vice versa. Read whether the question says displacement or distance before you integrate anything. Also expect interpretation points on FRQs, where you explain in a sentence what your integral means in context, with units.
Displacement is ∫v(t)dt and can be negative or zero; total distance is ∫|v(t)|dt and is never negative. If a particle moves right 10 and left 4, displacement is 6 but distance is 14. The two match only when v(t) doesn't change sign. On the exam, check where v(t) = 0 before deciding which integral to set up. Mixing these up is one of the most common point-losers on particle motion FRQs.
Displacement is the net change in position, calculated as the definite integral of velocity over the time interval.
Displacement can be negative or zero, because intervals where velocity is negative subtract from the total.
Displacement is not total distance traveled; distance uses ∫|v(t)|dt, and the two only agree when velocity never changes sign.
To find a particle's actual position, add the displacement to the initial position: x(b) = x(a) + ∫ₐᵇ v(t)dt.
This is the CED's accumulation idea (LO 8.3.A): the integral of a rate of change gives the net change of the quantity.
On BC, displacement extends to vector-valued motion in Topic 9.5, where you integrate each velocity component separately.
Displacement is the net change in an object's position over a time interval, found by integrating velocity: ∫ₐᵇ v(t)dt. It accounts for direction, so backward motion cancels forward motion.
No. Displacement is ∫v(t)dt and can be negative, while total distance is ∫|v(t)|dt and counts all motion as positive. If a particle moves right 10 units and left 4, displacement is 6 but distance traveled is 14.
Yes. If the particle ends up to the left of (or below) where it started, displacement is negative. It's zero if the particle returns to its starting point, even after lots of motion.
Add displacement to the given initial position: x(t) = x(0) + ∫₀ᵗ v(s)ds. The 2018 FRQ Q2 used exactly this setup, giving v(t) and the initial position x = −5 at t = 0.
Particle motion appears extremely consistently, including FRQ Q2 in both 2018 and 2024. Expect to compute displacement, position, and total distance from a given velocity function, usually with a calculator.