What mistakes do students make with Work done and energy transfer?

Assuming any movement means work is done by every force. Put it right by checking each force against the direction of motion. Using a distance that is not along the line of action of the force. Put it right by ensuring the distance used is in the same direction as the force. Treating a force at right angles to motion as doing work. Put it right by stating that perpendicular forces transfer no energy.

What are the exam tips for Work done and energy transfer in Combined Science AQA GCSE?

Sketch the force arrow and the displacement arrow to check they are in the same direction before calculating. If motion is perpendicular to a force, state that the work done by that force is zero rather than trying to calculate a value. Always read the question carefully to ensure the distance given is along the line of action of the force.

AQA · GCSE · Combined Science

Course version: 8464 · Version from Sept 2018

Work done and energy transfer: moved along the line of action of the force

Work is only done when the distance moved is along the line of action of the force.

Checked against the AQA 8464 specification (opens in a new tab) on 20 September 2026.

Point 4 of 13

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

Define the line of action as the straight line along which a force acts.
Identify whether the displacement is parallel, antiparallel or perpendicular to the force.
State that distance moved must be along the line of action of the force when calculating work done.
Explain that a force does zero work when the motion is perpendicular to its line of action.
Apply the idea to examples such as lifting a load vertically against weight or pushing horizontally along a floor.

Common mistakes and how to put them right

Assuming any movement means work is done by every force.
Put it right by checking each force against the direction of motion.
Using a distance that is not along the line of action of the force.
Put it right by ensuring the distance used is in the same direction as the force.
Treating a force at right angles to motion as doing work.
Put it right by stating that perpendicular forces transfer no energy.

Exam tips

Sketch the force arrow and the displacement arrow to check they are in the same direction before calculating.
If motion is perpendicular to a force, state that the work done by that force is zero rather than trying to calculate a value.
Always read the question carefully to ensure the distance given is along the line of action of the force.

Try the lesson

The start of the Work done and energy transfer: moved along the line of action of the force lesson, made from checked teaching notes for this specification point.

Have a go first

A pupil pushes a box with a force of 30 N. The box moves 4 m in the same direction as the force. What is the work done on the box?

Tip: press 1 to 4 to choose

Listen

Work is only done when the distance moved is along the line of action of the force. The line of action is the straight line through the force in the direction it pushes or pulls. For example, carrying a bag horizontally while gravity acts downwards means gravity does no work on the bag because motion is perpendicular to the force. Pushing a trolley 4 m with a 30 N horizontal force gives W = 30 N × 4 m = 120 J because the motion is along the force line. If the force and motion are at 90°, work done by that force is zero. A strong answer earns marks for these points. Define the line of action as the straight line along which a force acts. Identify whether the displacement is parallel, antiparallel or perpendicular to the force. State that distance moved must be along the line of action of the force when calculating work done. Explain that a force does zero work when the motion is perpendicular to its line of action. A common slip: Assuming any movement means work is done by every force. Instead, checking each force against the direction of motion. Exam tip: Sketch the force arrow and the displacement arrow to check they are in the same direction before calculating.

See it

A flowchart starting with a box saying a force acts along its line of action, which leads to a decision box asking how the direction of displacement compares with the force. Two branches leave the decision: one labelled parallel and one labelled antiparallel, both leading to a box saying the distance moved is along the line of action, which then leads to a box saying work done is calculated using the distance along the line of action. A third branch labelled perpendicular leads to a box saying motion is at 90 degrees to the force, which leads to a final box saying work done by that force is zero. — It shows how the direction of displacement relative to a force's line of action decides whether work is done, with perpendicular motion giving zero work.

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