The speed at which a person can walk, run or cycle depends on many factors…

The idea

Speed describes how far a person moves in a given time, but it is not a fixed personal constant. A child walking to school may average about 1 m/s, while a fit adult running may exceed 5 m/s; the same person slows on steep, muddy terrain or when carrying a heavy bag. Age affects strength, stamina and reaction time; fitness affects sustainable power output; terrain changes friction and gradient; and distance travelled matters because a short sprint can be faster than a long journey where fatigue builds. To compare journeys fairly, calculate speed using speed = distance ÷ time, keeping units consistent, for example 300 m ÷ 150 s = 2 m/s. Recognise that an average speed hides changes during the journey, so two people with equal averages may have moved very differently.

What earns the marks

• State that speed is calculated from distance travelled divided by time taken, and that the factors listed change either the distance covered, the time taken, or both.
• Explain that age can reduce maximum walking, running or cycling speed because of lower muscle strength, stamina or reaction time.
• Describe how terrain affects speed: uphill or rough ground increases resistance and reduces speed, while smooth, level ground allows faster movement.
• Explain that better fitness allows a person to sustain a higher speed for longer, especially over greater distances.
• Recognise that distance travelled influences average speed because fatigue and the need to pace oneself reduce speed on longer journeys.
• Use a calculation such as 1200 m ÷ 600 s = 2 m/s to show how a stated distance and time give a speed, and compare two sets of data.
• Interpret a distance–time graph by relating a steeper gradient to a higher speed and a shallower gradient to a lower speed.

Common mistakes and how to put them right

• Treating speed as a fixed value for a person.

  Put it right by stating that speed varies with conditions and by comparing calculated values from different journeys.

• Confusing speed with distance or time.

  Put it right by writing speed = distance ÷ time and checking that the answer has units of m/s or km/h.

• Assuming a longer distance always means a higher speed.

  Put it right by explaining that time must also be considered, since a long journey can have a low average speed.

• Ignoring unit conversion: correct this by converting km to m or minutes to seconds before dividing, for example 3 km = 3000 m and 5 min = 300 s.

Exam tips

• When asked to compare speeds, calculate both values using speed = distance ÷ time and quote the units with each answer.
• Link each named factor to a clear mechanism, such as terrain increasing friction or fitness increasing sustainable power, rather than listing factors alone.
• If a question gives a graph, read the gradient or use two points to find speed, and state that a steeper line means a faster speed.
• Show substitution clearly, for example speed = 400 m ÷ 80 s = 5 m/s, so the examiner can follow your method.