Calculate average speed

Supplied materials

• All measurements and observations below are supplied classroom examples. They are not data from actual learners or a claim about a particular real site.
• Paper or browser document; an ordinary calculator is optional.
• Rule: Average speed equals distance in meters divided by time in seconds. Formula: a/b. Variable key: a = total distance (m), b = elapsed time (s)
• Distinct worked inputs and result: A distinct route is 18 m in 3 s: 18/3=6 m/s average speed.
• Assessment case 1: Supplied case 1: total distance (m)=24; elapsed time (s)=6, using the explicitly named quantities. Average speed equals distance in meters divided by time in seconds. What result follows?
• Assessment case 2: Supplied case 2: total distance (m)=35; elapsed time (s)=5, using the explicitly named quantities. Average speed equals distance in meters divided by time in seconds. What result follows?
• Assessment case 3: Supplied case 3: total distance (m)=48; elapsed time (s)=8, using the explicitly named quantities. Average speed equals distance in meters divided by time in seconds. What result follows?
• Assessment case 4: Supplied case 4: total distance (m)=54; elapsed time (s)=9, using the explicitly named quantities. Average speed equals distance in meters divided by time in seconds. What result follows?
• Assessment case 5: Supplied case 5: total distance (m)=60; elapsed time (s)=12, using the explicitly named quantities. Average speed equals distance in meters divided by time in seconds. What result follows?
• Assessment case 6: Supplied case 6: total distance (m)=72; elapsed time (s)=8, using the explicitly named quantities. Average speed equals distance in meters divided by time in seconds. What result follows?

Learn the idea

Average speed is total distance divided by elapsed time. It does not reveal every instantaneous speed. Use total path length, not displacement, for this metric.

Average speed equals distance in meters divided by time in seconds. The formula in the supplied model is a/b. Variable key: a = total distance (m), b = elapsed time (s). Use total distance for speed. Time belongs in the denominator.

A distinct route is 18 m in 3 s: 18/3=6 m/s average speed. Average speed need not equal every moment’s speed. Track the quantity and unit before calculating. Explain the meaning of a positive, negative or fractional result when relevant. A numerical answer supports the stated model calculation; broader claims require the additional measurements and assumptions described here.

1. Name the measured quantities and their units before substituting values.
2. Write the stated rule and use the variable key to match each symbol to its explicitly named quantity.
3. Calculate each supplied case separately, keeping intermediate arithmetic and the result unit.
4. Explain the result in context and identify the assumption that would invalidate direct use of the rule.

Check your reasoning

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Take it further

Changed-input task: use the same stated model with total distance (m)=25; elapsed time (s)=6. Expected result: approximately 4.1666667 m/s. Explain what changes and keep this assumption: Average speed need not equal every moment’s speed.

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