OCR · GCSE · Physics
Course version: J249 · Version from Sept 2018
Motion: recall and apply: distance travelled (m) = speed (m/s) × time (s)
This equation links three quantities for motion at constant speed: distance travelled in metres equals speed in metres per second multiplied by time in seconds.
Checked against the OCR J249 specification (opens in a new tab) on .
- Point 1 of 14
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
This equation links three quantities for motion at constant speed: distance travelled in metres equals speed in metres per second multiplied by time in seconds. A cyclist moving at 6 m/s for 40 s covers 6 × 40 = 240 m. The equation can be rearranged: speed = distance ÷ time and time = distance ÷ speed. Before substituting, convert every quantity to the stated SI units, so 3 minutes becomes 180 s and 500 m stays in metres. Check the answer's size: a car at 20 m/s for 10 s should travel 200 m, not 2 m or 2000 m. In multiple-choice questions, work the calculation on paper first, then match your value to an option rather than choosing the option that looks familiar.
What earns the marks
- Selects the option equal to speed multiplied by time after converting time to seconds.
- Rearranges the relationship correctly when the question supplies distance and time and asks for speed.
- Converts minutes or hours to seconds before substituting into the equation.
- Rejects distractors produced by dividing instead of multiplying or by leaving time in minutes.
Common mistakes and how to put them right
Multiplies speed by time given in minutes without converting.
Put it right: Convert minutes to seconds first.
Divides distance by time when the question asks for distance.
Put it right: Multiply speed by time instead.
Ignores the unit labels in the options.
Put it right: Check that the chosen value carries the unit metre.
Exam tips
- Write the equation, substitute the numbers with units, then compute, so a slip is easy to spot.
- Convert all times to seconds and all distances to metres before any arithmetic.
- Estimate the answer first, for example 6 m/s for about 40 s is roughly 240 m, then pick the matching option.
Try the lesson
The start of the Motion: recall and apply: distance travelled (m) = speed (m/s) × time (s) lesson, made from checked teaching notes for this specification point.
Have a go first
A cyclist travels at a steady speed of 6 m/s for 10 s. What distance does the cyclist travel?
Listen
This equation links three quantities for motion at constant speed: distance travelled in metres equals speed in metres per second multiplied by time in seconds. A cyclist moving at 6 m/s for 40 s covers 6 × 40 = 240 m. The equation can be rearranged: speed = distance ÷ time and time = distance ÷ speed. Before substituting, convert every quantity to the stated SI units, so 3 minutes becomes 180 s and 500 m stays in metres. Check the answer's size: a car at 20 m/s for 10 s should travel 200 m, not 2 m or 2000 m. In multiple-choice questions, work the calculation on paper first, then match your value to an option rather than choosing the option that looks familiar. A strong answer earns marks for these points. Selects the option equal to speed multiplied by time after converting time to seconds. Rearranges the relationship correctly when the question supplies distance and time and asks for speed. Converts minutes or hours to seconds before substituting into the equation. Rejects distractors produced by dividing instead of multiplying or by leaving time in minutes. Exam tip: Write the equation, substitute the numbers with units, then compute, so a slip is easy to spot.
See it
Key words
Say what each word means before you turn the card.
distance travelled
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SI units
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rearranging
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unit conversion
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See every definition
- distance travelled
- Equals speed in metres per second multiplied by time in seconds for motion at constant speed.
- SI units
- The stated units are the metre, the metre per second and the second, and every quantity is converted to these before substituting.
- rearranging
- The equation can be rearranged so that speed equals distance divided by time and time equals distance divided by speed.
- unit conversion
- Before substituting, convert every quantity to the stated SI units, so minutes or hours become seconds and distances stay in metres.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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