Speed

Speed tells you how far something goes each second. On a distance–time graph, the slope (gradient) is the speed; a flat line means it has stopped. Acceleration is how quickly the speed changes.

Key facts

  • Speed = distance ÷ time.
  • Units: m/s, km/h.
  • Distance–time graph: steeper = faster; flat = stopped.
  • Acceleration = change in speed ÷ time (m/s²).

Worked examples

Example 1

A cyclist travels 300 m in 60 s. What is their speed?

  1. Divide. 300 ÷ 60 = 5
  2. So 5 m/s

Answer: 5 m/s

Example 2

A car goes from 0 to 20 m/s in 8 s. What is its acceleration?

  1. Change in speed. 20 − 0 = 20
  2. Divide by the time. 20 ÷ 8 = 2.5 m/s²

Answer: 2.5 m/s²