Beginner · 9 min
Speed and distance
Calculate average speed and use a constant speed to predict distance.
Average speed
Speed describes how quickly an object covers distance. Average speed is the total distance travelled divided by the total time taken. Include any stops in the total time. If distance is in metres and time is in seconds, speed is in metres per second (m/s). Average speed does not tell you how the speed changed during the journey. It uses distance along the whole route, even if you return to your starting point.
Worked example
A walker travels 60 m in 40 s. Average speed = 60 ÷ 40 = 1.5 m/s
Predict a distance
At a constant speed, equal time intervals cover equal distances. Multiply speed by time to find the distance travelled. Keep the time units consistent: a speed in metres per second needs a time in seconds. If the speed changes, this calculation still works when you use the average speed for that entire time interval.
Worked example
A trolley travels at a constant 2 m/s for 7 s. Distance = 2 × 7 = 14 m
Plan a journey
- On paper, plan a 200 m journey at an average speed of 2 m/s. Calculate the time required.
- Add a 20 s stop to that journey. Recalculate the average speed using the full journey time.