what's the difference between speed and velocity

Speed and velocity are both about how fast something moves, but velocity also cares about direction , while speed does not.
What’s the Difference Between Speed and Velocity?
Quick Scoop
- Speed : “How fast?” only, no direction.
- Velocity : “How fast and which way?” includes direction.
- Same magnitude, different meaning: 60 km/h is speed; 60 km/h east is velocity.
- You can have speed without actually “getting anywhere” (velocity zero in some cases).
Core Definitions (Short and Sweet)
- Speed : Rate at which an object covers distance over time, a scalar quantity (only magnitude).
* Formula: speed=distancetime\text{speed}=\frac{\text{distance}}{\text{time}}speed=timedistance.
- Velocity : Rate at which an object’s displacement (change in position) changes over time, a vector (magnitude + direction).
* Formula: velocity=displacementtime\text{velocity}=\frac{\text{displacement}}{\text{time}}velocity=timedisplacement.
Think of it this way: speed answers “How fast is it moving?”, velocity answers “How fast and in what direction is its position changing?”.
Key Differences at a Glance
| Feature | Speed | Velocity |
|---|---|---|
| Basic idea | How fast distance is covered. | [1][3][5]How fast and in which direction position changes. | [7][3][9][1][5]
| Quantity type | Scalar (magnitude only). | [3][1][5]Vector (magnitude + direction). | [7][1][3][5]
| Formula | Distance / time. | [9][1][3][5]Displacement / time. | [1][3][5][9]
| Direction | Not included. | [3][5][7]Direction is essential (e.g., “east”). | [5][7][3]
| Sign of value | Always non‑negative. | [1]Can be positive, negative, or zero (depending on direction and displacement). | [1]
| Typical unit | m/s, km/h, mph. | [3][5][1]Same units but with direction (e.g., m/s north). | [7][5][3]
| Zero value meaning | Object not moving at all. | [3]Either not moving or ends up back where it started over the time interval. | [9][5]
A Simple Story Example
Imagine you’re walking on a track:
- You walk 100 m forward, then 100 m back to where you started, in 200 seconds.
- Total distance = 200 m → average speed = 200 / 200 = 1 m/s.
* Total **displacement** = 0 m (you ended where you started) → average velocity = 0 / 200 = 0 m/s.
So in this little story, you clearly have speed , because you were moving, but your average velocity is zero because your overall position didn’t change.
Why It Matters (Different Viewpoints)
- Physics viewpoint : Velocity is used when direction changes matter (projectiles, orbits, circular motion, etc.), while speed is fine when you only care about “how fast”.
- Everyday viewpoint : Road signs and fitness apps usually show speed (km/h, mph) because most people just want a quick sense of how fast they’re going.
- Exam viewpoint : Many textbook and exam questions explicitly ask you to state that speed is scalar and velocity is vector, and to use distance vs. displacement correctly in formulas.
Quick TL;DR
- If direction doesn’t matter → you’re talking about speed.
- If direction does matter → you’re talking about velocity.
Bottom note: Information gathered from public forums or data available on the internet and portrayed here.