Speed

    OCR
    GCSE

    Speed is defined as the rate of change of distance and is a scalar quantity, distinguished from velocity by the absence of directional components. Candidates must demonstrate proficiency in calculating average speed using the equation v = s/t, rearranging the formula, and performing unit conversions between m/s, km/h, and mph. Analysis of motion requires the interpretation of distance-time graphs, where the gradient represents speed, and the ability to distinguish between uniform and non-uniform motion. Mastery involves applying these concepts to experimental contexts, such as using light gates or ticker timers to measure rapid motion with precision.

    0
    Objectives
    3
    Exam Tips
    4
    Pitfalls
    5
    Key Terms
    5
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for the correct substitution of values into the equation speed = distance / time.
    • Credit the calculation of the gradient on a distance-time graph to represent speed.
    • Award 1 mark for stating that speed is a scalar quantity, distinct from velocity which is a vector.
    • Credit the correct conversion of units, specifically from km/h or minutes to m/s or seconds, before final calculation.
    • Award 1 mark for recalling typical speeds (e.g., walking ~1.5 m/s, sound ~330 m/s) when asked to estimate.

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for the correct substitution of values into the equation speed = distance / time.
    • Credit the calculation of the gradient on a distance-time graph to represent speed.
    • Award 1 mark for stating that speed is a scalar quantity, distinct from velocity which is a vector.
    • Credit the correct conversion of units, specifically from km/h or minutes to m/s or seconds, before final calculation.
    • Award 1 mark for recalling typical speeds (e.g., walking ~1.5 m/s, sound ~330 m/s) when asked to estimate.

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When asked to 'Estimate' a speed, use the specific values listed in the specification (e.g., walking ~1.5 m/s, cycling ~6 m/s) as your baseline.
    • 💡For 4-mark calculation questions, explicitly state the formula, substitution, and unit conversion as separate steps to secure method marks even if the final answer is wrong.
    • 💡Check the axis labels immediately; do not confuse the gradient of a distance-time graph (speed) with the gradient of a velocity-time graph (acceleration).

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Calculating the arithmetic mean of two different speeds to find average speed, rather than dividing total distance by total time.
    • Inverting the gradient calculation on distance-time graphs (calculating run over rise instead of rise over run).
    • Failing to draw a tangent to calculate instantaneous speed on a curved distance-time graph, often attempting to use a chord instead.
    • Confusing the units of time, such as treating 1.5 hours as 1 hour 50 minutes instead of 90 minutes.

    Study Guide Available

    Comprehensive revision notes & examples

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    Key Terminology

    Essential terms to know

    Scalar nature of speed versus vector nature of velocity
    Quantitative relationship: speed = distance / time
    Graphical analysis: Distance-time graphs and gradients
    Measurement techniques: Light gates, stopwatches, and ticker timers
    Typical speeds in everyday contexts (walking, running, sound, light)

    Likely Command Words

    How questions on this topic are typically asked

    Calculate
    Estimate
    Describe
    Explain
    Plot
    Determine

    Practical Links

    Related required practicals

    • •{"code":"P2.1 Investigation","title":"Measuring speed of a trolley","relevance":"Use of light gates or ticker timers to determine average vs instantaneous speed"}

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