Work Done by a Force
Work is done by a force when the force causes displacement of an object in the direction of the force or with a component along the displacement.
Practice This ConceptMain explanation
Teacher explanation
In school-level problems, work is calculated as force multiplied by displacement in the direction of force. If a force is applied but the object does not move, work done is zero. If the force and displacement are at an angle, only the component of force along displacement contributes to work.
Example
If a student pushes a box with a force of 20 N and the box moves 3 m in the same direction, work done is 20 × 3 = 60 J.
Simple analogy
Work needs force plus displacement.
Common confusion
Students often write work as force × time or calculate work even when the object has not moved.
Exam tip
Always check two things before calculating work: force must act, and displacement must occur along the force or its component.
Study the work done by a force diagram carefully
Use the labelled diagram to keep work done by a force clear in short answers and revision.
What this diagram makes clear
This diagram keeps the labels and direction of work done by a force in the right order.
Where this helps in exams
Use this for labelled diagram work and short exam answers on work done by a force.
Revision cue
Revise work done by a force through the labels before writing the answer.
Answer writing and exam use
1-mark use
Write the exact meaning of work done by a force in one clean line.
2-mark use
Define work done by a force and add one example or condition.
3-mark use
Explain work done by a force, show the method or example, and mention the common mistake.
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