Work done and energy transfer

    AQA
    GCSE

    Work done is formally defined as the quantity of energy transferred when a force moves an object through a distance along the line of action of the force. Candidates must apply the quantitative relationship $W = F s$, explicitly recognizing that 1 Joule is equivalent to 1 Newton-metre. Analysis must extend to energy dissipation, specifically explaining how work done against frictional forces results in a rise in the thermal energy of the object and surroundings. Proficiency requires the manipulation of the equation to solve for force or distance and the rigorous conversion of non-standard units (e.g., kN, cm) prior to substitution.

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    Objectives
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    Exam Tips
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    Pitfalls
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    Key Terms
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    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for stating that work done is equal to energy transferred in the given context
    • Award 1 mark for correct substitution of values into the equation $W = F s$ showing conversion of distance to metres
    • Credit responses that explicitly link work done against frictional forces to an increase in the temperature of the object or surroundings
    • Award 1 mark for the correct unit, accepting either Joules (J) or Newton-metres (Nm) as equivalent

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that work done is equal to energy transferred in the given context
    • Award 1 mark for correct substitution of values into the equation $W = F s$ showing conversion of distance to metres
    • Credit responses that explicitly link work done against frictional forces to an increase in the temperature of the object or surroundings
    • Award 1 mark for the correct unit, accepting either Joules (J) or Newton-metres (Nm) as equivalent

    Examiner Tips

    Expert advice for maximising your marks

    • 💡Treat the terms 'work done' and 'energy transferred' as interchangeable; if asked for one, you can calculate the other
    • 💡When calculating work done against gravity (lifting), remember the Force ($F$) is the Weight ($mg$), not just the mass
    • 💡For braking distance questions, equate work done by brakes ($F \times s$) to the initial kinetic energy ($\frac{1}{2} m v^2$)

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Failing to convert distance measurements from centimetres (cm) or kilometres (km) into metres (m) prior to calculation
    • Confusing the mass of an object (kg) with the force/weight (N) required to lift it, neglecting to multiply by gravitational field strength ($g$)
    • Describing energy as being 'lost' or 'used up' due to friction, rather than 'dissipated' or 'transferred to thermal stores'

    Key Terminology

    Essential terms to know

    Likely Command Words

    How questions on this topic are typically asked

    Calculate
    Explain
    State
    Describe
    Suggest

    Practical Links

    Related required practicals

    • •{"code":"General Practical","title":"Investigation of personal power and work done (climbing stairs)","relevance":"Calculating work done against gravity"}
    • •{"code":"General Practical","title":"Dragging blocks up ramps","relevance":"Comparing work done lifting vs dragging (efficiency)"}

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