Speed

Speed tells you how quickly something moves by comparing how far it travels with how long it takes. If the same distance is covered in less time, the speed is higher; if more time is needed for the same distance, the speed is lower. This works because speed is a rate: it measures distance per unit time.

Use this formula whenever you know the distance travelled and the time taken, such as for walking, driving, running, or cycling. It is also useful in travel problems and in checking whether something moved at a steady rate.

• dividing time by distance instead of distance by time
• using mismatched units such as kilometres with minutes without converting
• forgetting that speed must include units, like m/s or km/h