Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
Describe how to measure the work done by a force and understand that…
Full specification wording
Topic 8 – Energy – forces doing work: 8.5 Describe how to measure the work done by a force and understand that energy transferred (joule, J) is equal to work done (joule, J)
Work done by a force is measured by multiplying the force by the distance moved along the line of the force: W = F × s.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 5 of 15
Study notes
From the checked teaching notes for this specification point.
The idea
Work done by a force is measured by multiplying the force by the distance moved along the line of the force: W = F × s. In practice, measure the force with a newton meter and the displacement with a ruler or tape measure, keeping the motion parallel to the applied force. The unit of work done is the joule, J, because 1 N × 1 m = 1 J. Energy transferred to or from the system equals the work done, so both quantities are measured in joules and one joule of work transfers one joule of energy. A 20 N force moving an object 3 m along its line of action does 60 J of work and transfers 60 J of energy. Recognise the equation, the measuring instruments and the equivalence of the two quantities.
What earns the marks
- States that work done is calculated as force multiplied by distance moved along the line of action of the force.
- Selects a newton meter to measure the force and a ruler or tape measure to measure the distance moved.
- States that the unit of work done is the joule, J, since 1 N × 1 m = 1 J.
- States that the energy transferred to or from the system equals the work done, both measured in joules.
- Applies W = F × s to a numerical case, for example 20 N × 3 m = 60 J.
Common mistakes and how to put them right
Multiplies force by a distance measured at right angles to the force.
Put it right: Measure the distance moved along the line of action of the force.
Uses newtons for work done.
Put it right: State that work done and energy transferred are both in joules.
Treats work done and energy transferred as different quantities with different units.
Put it right: State that they are equal and both in joules.
Omits the unit when giving a numerical answer.
Put it right: State the value with J.
Exam tips
- Write the equation W = F × s before substituting values so units stay consistent.
- Check that the distance given is along the force; if not, resolve the force or the displacement.
- Give numerical answers with the unit J and, where asked, state the energy transferred as equal to the work done.
- Recall that 1 J = 1 N m, which confirms the unit of work done.
Try the lesson
The start of the Topic 8 – Energy – forces doing work: 8.5 Describe how to measure the work done by a force and understand that energy transferred (joule, J) is equal to work done (joule, J) lesson, made from checked teaching notes for this specification point.
Have a go first
A box is pushed along a floor with a steady force, and the force acts in the same direction as the movement. What is the unit of the work done by the force?
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