Short answer
Velocity tells you how fast and in what direction position changes. Acceleration tells you how velocity changes over time. A vehicle can be moving fast with zero acceleration if its velocity stays constant, or accelerate while turning at a constant speed. 1 2
Velocity says how position is changing; acceleration says how velocity is changing.
On this page
At a glance
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| Question | Velocity | Acceleration |
|---|---|---|
| Tracks change in | Position | Velocity |
| SI unit | Meters per second | Meters per second squared |
| Direction matters? | Yes | Yes |
The table summarizes the cited definitions and the article’s stated scope. 1 2
What each thing is
Velocity. The rate and direction of change in position over time. 1
Acceleration. The rate and direction of change in velocity over time. 2
Key differences
Average velocity is displacement divided by time; average acceleration is velocity change divided by time. Because velocity includes direction, changing direction counts as acceleration even when the speedometer reading stays the same. 1 2
How to tell them apart
Ask which quantity changes. If a car covers distance east at an unchanging 20 m/s, it has velocity but zero acceleration in that idealization. If it speeds up, slows down or turns, velocity changes and it accelerates. 1 2
Where they overlap
Both are vector quantities used to describe one motion. Acceleration influences future velocity; velocity influences future position. 1 2
Edge cases
At an instant, velocity can be zero while acceleration is nonzero, as at the highest point of a vertically tossed ball. Negative acceleration does not automatically mean slowing down; sign depends on the chosen coordinate direction. 1 2
Why the distinction exists
Physics separates the first and second rates of change so motion can be predicted rather than described by speed alone. 1 2
Common misconceptions
Acceleration is not simply “moving fast.” Braking and turning both involve acceleration in the physics sense. 1 2
Examples
A car cruising straight at a constant speed has velocity and approximately zero acceleration. As it enters a curve at the same speed, its direction changes and it accelerates. 1 2
Sources
Sources checked October 3, 2026.
- OpenStax — Time, Velocity, and Speed. Average velocity.
- OpenStax — Acceleration. Average acceleration.