Acceleration

    OCR
    GCSE

    Acceleration is defined as the rate of change of velocity per unit time, distinguishing it as a vector quantity that accounts for changes in both speed and direction. Analysis of motion requires the application of kinematic equations, specifically relating initial velocity, final velocity, displacement, and time, alongside the interpretation of velocity-time graphs where the gradient represents acceleration. Understanding acceleration is fundamental to Newtonian mechanics, serving as the bridge between kinematic description and dynamic cause via Newton's Second Law (F=ma).

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    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 stating that acceleration is the rate of change of velocity
    • Credit substitution of correct values into the equation v^2 - u^2 = 2as, ensuring velocities are squared
    • Award 1 mark for calculating the gradient of a velocity-time graph to determine acceleration
    • Credit the correct unit m/s^2 in final answers; reject m/s
    • Award 1 mark for identifying deceleration as a negative value when the direction of motion is positive

    Example Examiner Feedback

    Real feedback patterns examiners use when marking

    • "You correctly identified the formula, but check your units — acceleration is measured in m/s^2, not m/s."
    • "Good use of the graph, but remember that acceleration is the gradient (change in y / change in x), not just reading the y-axis."
    • "You forgot to square the velocities in the equation v^2 - u^2 = 2as. Correct this to find the right distance."
    • "Excellent calculation. To secure top marks, explicitly state the direction of the acceleration if it is a vector quantity."

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that acceleration is the rate of change of velocity
    • Credit substitution of correct values into the equation v^2 - u^2 = 2as, ensuring velocities are squared
    • Award 1 mark for calculating the gradient of a velocity-time graph to determine acceleration
    • Credit the correct unit m/s^2 in final answers; reject m/s
    • Award 1 mark for identifying deceleration as a negative value when the direction of motion is positive

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When using v^2 - u^2 = 2as, ensure you square the velocities *before* subtracting them; this is the most common calculation error.
    • 💡In velocity-time graphs, remember that a straight line represents constant acceleration, while a curve represents changing acceleration requiring a tangent.
    • 💡Always check if the object starts from rest (u=0) or comes to a stop (v=0) to simplify your calculations immediately.

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing the unit of acceleration (m/s^2) with the unit of velocity (m/s) or speed
    • Incorrectly rearranging v^2 - u^2 = 2as, particularly failing to square the velocity terms before subtraction
    • Calculating the gradient of a distance-time graph (speed) instead of a velocity-time graph (acceleration)
    • Neglecting the negative sign for deceleration, leading to incorrect vector sums

    Key Terminology

    Essential terms to know

    Rate of change of velocity and vector nature
    Graphical analysis (velocity-time graphs)
    Uniform acceleration equations (suvat)
    Acceleration due to gravity and free fall
    Newton's Second Law relationship (F=ma)

    Likely Command Words

    How questions on this topic are typically asked

    Calculate
    Describe
    Explain
    Estimate
    Analyse

    Practical Links

    Related required practicals

    • •{"code":"PAG P3","title":"Investigation of Motion","relevance":"Measuring acceleration using light gates or ticker timers to verify F=ma"}

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