Work Done

    OCR
    GCSE

    Work done is defined as the measure of energy transfer that occurs when a force moves an object through a distance. The magnitude is calculated as the product of the force and the displacement along the line of action of the force ($W = Fs$). Candidates must recognize the equivalence between work done and energy transferred, where 1 Joule equals 1 Newton-metre. Mastery requires applying this principle to scenarios involving friction, where mechanical work dissipates as thermal energy, and gravitational fields, where work transforms into potential energy.

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    Objectives
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    Exam Tips
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    Pitfalls
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    Key Terms
    5
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for recalling the equation: Work done = Force × distance (or W = F × d)
    • Credit correct substitution of values, specifically awarding marks for converting distance into metres (m) and force into Newtons (N)
    • Award 1 mark for stating that 1 Joule is equivalent to 1 Newton-metre
    • In contexts involving friction, credit responses that link work done to the dissipation of energy as thermal energy (heat) to the surroundings
    • Award 1 mark for the final calculated answer with correct significant figures and unit (J or Nm)

    Example Examiner Feedback

    Real feedback patterns examiners use when marking

    • "You correctly identified the formula, but check your units — did you convert cm to m?"
    • "Remember that mass is not force. You must calculate Weight = mass × g before finding Work Done when lifting"
    • "Good calculation, but you must specify that the energy lost to friction becomes thermal energy"
    • "You have calculated the energy transferred correctly; to get full marks, link this to the power rating as requested"

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for recalling the equation: Work done = Force × distance (or W = F × d)
    • Credit correct substitution of values, specifically awarding marks for converting distance into metres (m) and force into Newtons (N)
    • Award 1 mark for stating that 1 Joule is equivalent to 1 Newton-metre
    • In contexts involving friction, credit responses that link work done to the dissipation of energy as thermal energy (heat) to the surroundings
    • Award 1 mark for the final calculated answer with correct significant figures and unit (J or Nm)

    Examiner Tips

    Expert advice for maximising your marks

    • 💡Treat the terms 'Work Done' and 'Energy Transferred' as synonymous; if asked for energy and given force/distance, use W = F × d
    • 💡When calculating work done against gravity (lifting), always calculate Weight (W = mg) first if only mass is provided
    • 💡Pay close attention to prefixes in units (e.g., kJ, MN); conversion marks are frequently lost here in high-tariff calculation questions

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Substituting mass (kg) directly into the equation instead of Weight/Force (N); candidates fail to multiply mass by gravitational field strength (g)
    • Neglecting to convert distances given in centimetres (cm) or kilometres (km) into the standard SI unit of metres (m)
    • Assuming work is done when an object is held stationary; candidates fail to recognise that if distance is zero, work done is zero
    • Confusing the direction of force; incorrectly calculating work done when the force is perpendicular to the direction of motion

    Study Guide Available

    Comprehensive revision notes & examples

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    Key Terminology

    Essential terms to know

    Equivalence of work done and energy transferred
    Calculation of work using W = Fs
    Work done against frictional forces (thermal dissipation)
    Work done against gravity (GPE)

    Likely Command Words

    How questions on this topic are typically asked

    Calculate
    Explain
    State
    Describe
    Suggest

    Practical Links

    Related required practicals

    • •{"code":"PAG P5","title":"Personal Power / Stair Climb","relevance":"Calculating work done against gravity (weight × vertical height) to determine human power output"}
    • •{"code":"General Practical","title":"Dragging blocks","relevance":"Measuring force via newton-meter and distance to calculate work done against friction"}

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