Velocity and acceleration

    AQA
    GCSE

    Velocity is a vector quantity defined as the rate of change of displacement, distinct from speed which is a scalar magnitude. Acceleration is the rate of change of velocity, quantified mathematically as the gradient of a velocity-time graph, while the area under such a graph represents displacement. Mastery of this topic requires the application of equations of uniform motion and the rigorous interpretation of graphical data to analyse kinematic 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 acceleration is the rate of change of velocity, not just change in speed
    • Credit the calculation of acceleration as the gradient of the tangent for non-uniform motion on a velocity-time graph
    • Award marks for splitting the area under a velocity-time graph into geometric shapes (rectangles and triangles) to calculate total displacement
    • For v² - u² = 2as, award 1 mark for correct substitution and 1 mark for the final answer with correct significant figures
    • Credit responses that explicitly identify deceleration as a negative value when calculating acceleration

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that acceleration is the rate of change of velocity, not just change in speed
    • Credit the calculation of acceleration as the gradient of the tangent for non-uniform motion on a velocity-time graph
    • Award marks for splitting the area under a velocity-time graph into geometric shapes (rectangles and triangles) to calculate total displacement
    • For v² - u² = 2as, award 1 mark for correct substitution and 1 mark for the final answer with correct significant figures
    • Credit responses that explicitly identify deceleration as a negative value when calculating acceleration

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When asked to 'Show that' an acceleration has a specific value, you must show the substitution into the equation clearly before writing the final answer
    • 💡Annotate velocity-time graphs directly on the paper, drawing triangles to calculate gradients or breaking areas into rectangles and triangles for displacement
    • 💡Check the axis labels immediately; a curve on a distance-time graph represents acceleration, whereas a straight line on a velocity-time graph represents constant acceleration

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing velocity-time graphs with distance-time graphs, interpreting a horizontal line as 'stationary' rather than 'constant velocity'
    • Applying the constant speed formula v = s/t to situations involving acceleration, instead of using the appropriate equations of motion
    • Neglecting to square the velocity terms when using the uniform acceleration equation v² - u² = 2as
    • Failing to convert units (e.g., km/h to m/s) before substitution, leading to order-of-magnitude errors

    Key Terminology

    Essential terms to know

    Likely Command Words

    How questions on this topic are typically asked

    Calculate
    Determine
    Describe
    Explain
    Show that

    Practical Links

    Related required practicals

    • •{"code":"Required Practical 7","title":"Investigation of Force and Acceleration","relevance":"Experimental verification of Newton's Second Law involving measurement of acceleration"}

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