Work, Energy and Power | OCR A-Level Physics A (H556)
Work, Energy and Power
- 42 questions
- 3 subtopics
- Module 3: Forces and motion
- Paper 1 and Paper 3
Work as energy transferred, the interchange of kinetic and potential energy, and the rate at which energy is transferred..
It covers work done and conservation of energy, kinetic and gravitational potential energy and power and efficiency.
Sample questions from Work, Energy and Power
Answer each one closed book first, then open the answer.
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Work done and conservation of energy
In the equation W = Fx cos θ, what does the angle θ represent?
Show the answer
θ is the angle between the force vector and the displacement vector. -
Work done and conservation of energy
List four different forms of energy.
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Any four from: kinetic, gravitational potential, elastic potential, thermal, chemical, electrical, nuclear, and electromagnetic radiation. -
Kinetic and gravitational potential energy
When deriving Eₖ = ½mv², how is the equation v² = u² + 2ax rearranged to express displacement?
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It is rearranged to give x = (v² − u²)/(2a). -
Kinetic and gravitational potential energy
How is work done calculated when lifting an object through a height h at constant velocity?
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Work done is W = Fh = mgh. -
Power and efficiency
State the equation for power delivered by a force moving an object at constant velocity.
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P = Fv, where F is the force and v is the velocity. -
Power and efficiency
Calculate the efficiency when useful output energy = 1305 J, total input energy = 6026 J.
Show the answer
Efficiency = (1305 ÷ 6026) × 100 = 21.7 %.
The 3 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Work done and conservation of energy | Recall questions on work done and its unit, W = Fx cos θ and calculations with it, the principle of conservation of energy, forms of energy and how energy transfer relates to work done. | 10 |
| Kinetic and gravitational potential energy | Recall questions on kinetic energy and gravitational potential energy, their equations, calculations and derivations from first principles, and the exchange between them for a freely falling object. | 16 |
| Power and efficiency | Recall questions on power and the watt, P = W/t and P = Fv with their derivation and calculations, efficiency in terms of energy and power, and why efficiency is always below 100%. | 16 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Physics A Active Recall Guide
Every topic, not just this one. 1,862 questions with their answers.