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What is speed?

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Quick answer

Speed is how fast something is moving — the distance it covers in a given amount of time. A car going 60 kilometres per hour covers 60 km each hour. Speed has size but no direction, which is what separates it from velocity.

Key things to understand

  1. Speed = distance ÷ time. Its units are things like metres per second (m/s) or kilometres per hour (km/h).
  2. It's a scalar — it has magnitude (a number) but no direction.
  3. Average speed is total distance over total time; instantaneous speed is how fast you're going at one moment (what a speedometer shows).
  4. Velocity is speed with a direction — 60 km/h north is a velocity; 60 km/h is just a speed.

People also ask

What's the difference between speed and velocity?
Speed only tells you how fast (a number); velocity tells you how fast AND in which direction. Velocity is speed with direction attached.
What is average speed?
Total distance travelled divided by the total time taken. Drive 120 km in 2 hours and your average speed is 60 km/h, even if you sped up and slowed down along the way.
How is speed measured?
By dividing distance by time. A speedometer measures instantaneous speed — your speed at that exact moment.