Velocity

    OCR
    GCSE

    Velocity is a vector quantity defined as the rate of change of displacement, distinct from speed which is a scalar magnitude. Mastery requires the interpretation of displacement-time graphs where the gradient represents velocity, and velocity-time graphs where the area under the curve represents displacement. Candidates must apply equations of motion to calculate average and instantaneous velocity, strictly adhering to sign conventions to indicate direction in one-dimensional systems.

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

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for stating that velocity is a vector quantity having both magnitude and direction
    • Award 1 mark for calculating acceleration as the gradient of a velocity-time graph
    • Credit responses that determine distance travelled by calculating the area under a velocity-time graph
    • Award 1 mark for correct substitution into the equation v² - u² = 2as
    • Candidates must identify that a horizontal line on a velocity-time graph represents constant velocity, not stationary

    Example Examiner Feedback

    Real feedback patterns examiners use when marking

    • "You correctly calculated the gradient, but check your units — velocity is m/s, acceleration is m/s²"
    • "Good use of the equation. To improve, explicitly state the rearrangement before substituting values"
    • "You confused the graph types here; remember that area under a velocity-time graph is distance, not acceleration"
    • "Excellent tangent drawing. Ensure you pick points far apart on your tangent line to minimize calculation error"

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that velocity is a vector quantity having both magnitude and direction
    • Award 1 mark for calculating acceleration as the gradient of a velocity-time graph
    • Credit responses that determine distance travelled by calculating the area under a velocity-time graph
    • Award 1 mark for correct substitution into the equation v² - u² = 2as
    • Candidates must identify that a horizontal line on a velocity-time graph represents constant velocity, not stationary

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When asked to 'Determine' from a graph, show your working directly on the graph (e.g., drawing a triangle for the gradient)
    • 💡Check the axes carefully: a horizontal line means 'stationary' on a distance-time graph but 'constant velocity' on a velocity-time graph
    • 💡For Higher Tier, remember to draw a tangent to the curve on a distance-time graph to find instantaneous speed

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing displacement with distance, particularly when an object changes direction
    • Calculating the gradient of a distance-time graph to find acceleration instead of speed
    • Failing to convert units, such as km/h to m/s, before substituting into equations
    • Assuming a negative velocity implies slowing down rather than moving in the opposite direction

    Study Guide Available

    Comprehensive revision notes & examples

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    Key Terminology

    Essential terms to know

    Vector vs Scalar distinction (Displacement vs Distance)
    Graphical analysis of motion (Gradients and Areas)
    Average vs Instantaneous velocity
    Equations of uniform motion

    Likely Command Words

    How questions on this topic are typically asked

    Calculate
    Describe
    Explain
    Determine
    Estimate

    Practical Links

    Related required practicals

    • •{"code":"P2.3","title":"Measuring speed","relevance":"Using light gates or stopwatches to determine velocity of a trolley"}

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