Speed vs Velocity: Scalar vs Vector
Learn the difference between speed and velocity with two worked examples and the most common mistake.
The difference
- Speed = distance ÷ time
- Velocity = displacement ÷ time
Distance is the total path length. Displacement is the straight-line change in position, with direction.
Example 1
A car drives 60 km east in 1.5 h. Find speed and velocity.
- Speed = 60 ÷ 1.5 = 40 km/h
- Velocity = 40 km/h east
40 km/h, 40 km/h east
Example 2
A runner does one full 400 m lap in 80 s. Find average speed and average velocity.
- Speed = 400 ÷ 80 = 5 m/s
- Displacement = 0 (back at the start)
- Velocity = 0 ÷ 80 = 0 m/s
Speed 5 m/s, velocity 0
Common mistake
Velocity is just speed with a different name
Speed is a scalar (no direction). Velocity is a vector (needs direction).
Average speed can never be negative. Velocity can, depending on your chosen direction.
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