Velocity
How fast your position changes, with a direction. Average velocity is displacement divided by time.
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Analogy
Speed is the number on the speedometer. Velocity also says which way you are going.
Example
v = displacement / timev = 100 m / 20 sv = 5 m/s east
In practice
A runner covers 100 m east in 20 s. Her average velocity is 5 m/s east.
Practice
Flashcards
- What is the difference between speed and velocity?Speed has size only. Velocity has size and direction.
Interview questions
- Explain why a car going round a bend at steady speed is still accelerating.
- Acceleration is a change in velocity
- Direction changes even if speed does not
- Acceleration points toward the centre of the bend
Questions people ask
What is the difference between average and instantaneous velocity?
Average velocity is total displacement divided by total time for a whole trip. Instantaneous velocity is the velocity at one exact moment, like the reading you would get from a perfect speedometer that also shows direction. On a graph it is the slope at a point.
Why is velocity measured in metres per second?
Velocity is a change in position, measured in metres, divided by the time it takes, measured in seconds. So the SI unit is metres per second. To convert from km/h to m/s, divide by 3.6. For example, 36 km/h equals 10 m/s.