Energy
Lesson overview
This lesson introduces the core physics idea, the useful equipment and the calculation or data skills used on this page.
What you will learn
Mechanical energy examples supplied on this page
Use lifting, pushing, climbing and machine examples to practise connecting force, distance, work and power.
Work done, power and energy transfer infographic
Clear explanation
Work is done when a force causes movement in the direction of the force. Work done is equal to energy transferred, so both are measured in joules.
The equation work done = force x distance uses the distance moved in the direction of the force. If the force and movement are not in the same direction, GCSE questions usually make the required distance clear.
Power is the rate of energy transfer. A more powerful machine transfers the same energy in less time, or more energy in the same time.
Worked examples
Work done lifting a box
A student lifts a box with a force of 80 N through 1.5 m.
work done = force x distance
work done = 80 x 1.5
Quick checks
Choose an answer, then check your thinking.
1. What is work done measured in?
2. What does power measure?
Practice questions
Question 1
A force of 50 N moves an object 4 m. Calculate work done.
Reveal answer and marking guidance
Answer: 200 J.
Marking: Credit W = F x s and 50 x 4 = 200 J.
Question 2
A machine transfers 900 J in 30 s. Calculate power.
Reveal answer and marking guidance
Answer: 30 W.
Marking: Credit P = E ÷ t and 900 ÷ 30 = 30 W.
Question 3
Why is work done equal to energy transferred?
Reveal answer and marking guidance
Answer: Because a force moving an object transfers energy mechanically.
Marking: Credit mechanical energy transfer by a force over a distance.
Question 4
Two motors lift the same load through the same height. Motor A takes less time. Which has greater power?
Reveal answer and marking guidance
Answer: Motor A.
Marking: Credit same energy transferred in less time gives greater power.
Practice ladder
Answers and marking guidance
The exact practice answers are hidden under each question so you can try first. For this lesson, marks come from using the correct physics model, choosing the right equation where needed, keeping units with values, and explaining changes with precise words such as transfer, resultant force, acceleration, evidence and uncertainty.
Common mistakes
- Using distance travelled when it is not along the force direction.
- Confusing watts with joules.
- Saying power is the total energy rather than rate of transfer.
- Forgetting that work done needs movement.
Extension challenge
Compare a slow lift and a fast lift that raise the same mass through the same height, using energy and power language.
Reveal answer
Example answer: A strong extension response names the physics model, uses accurate units and explains why the evidence supports the conclusion.
Exam-board guidance
Short board notes only. Learn the core physics above first.
AQA GCSE Physics
AQA GCSE Physics: often rewards clear physics explanations, correct equations, units and practical evidence for work done, power and mechanical energy transfer.
OCR GCSE Physics
OCR GCSE Physics: often values precise definitions, clear working, graph interpretation and links between models and evidence.
Pearson Edexcel GCSE Physics
Pearson Edexcel GCSE Physics: often combines the concept with equation use, data handling and practical interpretation.
Eduqas GCSE Physics
Eduqas GCSE Physics: learn the core explanation and practise applying it to unfamiliar contexts, data and practical questions.
WJEC Wales
WJEC Wales: often expects accurate terms, units and evidence-based explanations using the shared physics idea.
CCEA GCSE Physics
CCEA GCSE Physics: connect the idea to your current unit and use the same practical method language your class uses.
Next lesson
Next, continue with Radiation Uses, Irradiation and Contamination.