CCEA A Level Physics
CCEA A Level Physics 1.8 Work Done, Potential and Kinetic Energy Exam Questions
Free CCEA A Level Physics revision for 1.8 Work Done, Potential and Kinetic Energy: what you need to know, common mistakes and exam-style questions with answers. Covers work done, gravitational potential energy, kinetic energy, conservation of energy, power, efficiency and energy use in society.
Practise 1.8 Work Done, Potential and Kinetic Energy with past papers
Once you have learnt this topic, find the 1.8 Work Done, Potential and Kinetic Energy questions in real CCEA A Level Physics past papers and mark them with the mark scheme. Doing lots of real questions is the quickest way to learn how examiners ask about each idea.
StemUp mark scheme flashcards
A-Level Physics Flashcards for 2027 Onwards
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Then test yourself with the questions on this page.
From £10.99View flashcards
About CCEA A Level Physics 1.8 Work Done, Potential and Kinetic Energy
This section of Unit AS 1: Forces, Energy and Electricity connects forces to energy. You need to define work done as force times displacement in the direction of the force, calculate changes in gravitational potential energy and kinetic energy, and apply conservation of energy to falling objects, ramps and pendulums. Power and efficiency follow, along with the wider issue of energy conservation in society. The ideas link back to momentum (collisions where kinetic energy changes) and forward to electrical power and thermal physics. Typical questions ask for a definition, a speed found by equating potential and kinetic energy, and an efficiency calculation for a motor.
What you need to know
- Work done Work done = force x displacement in the direction of the force, W = Fs cos θ. Unit joule (J): 1 J is the work done when a force of 1 N moves its point of application 1 m in the direction of the force.
- Potential energy Change in gravitational potential energy Δp.e. = mgΔh, valid near the Earth's surface where g is constant.
- Kinetic energy k.e. = 1/2 mv^2. It can be derived from W = Fs, F = ma and v^2 = u^2 + 2as for an object starting from rest.
- Conservation of energy Energy cannot be created or destroyed, only transferred. With no friction, loss in p.e. equals gain in k.e., so v = square root of 2gh for an object falling from rest.
- Power Power is the rate of doing work or transferring energy, P = W/t, unit watt. For a force moving at constant velocity, P = Fv.
- Efficiency Efficiency = useful energy (or power) output / total energy (or power) input, as a decimal or percentage. Energy conservation in society means reducing waste through insulation, efficient appliances and transport.
Common mistakes in 1.8 Work Done, Potential and Kinetic Energy
- Using the distance moved rather than the displacement in the direction of the force; only the component along the force counts.
- Forgetting to square the velocity in 1/2 mv^2, or squaring the whole of 1/2 mv.
- Giving an efficiency greater than 1 or 100 percent; check that output is smaller than input.
- Confusing energy and power; power is energy per second, so a 2 kW heater transfers 2000 J every second.
Try three 1.8 Work Done, Potential and Kinetic Energy exam-style questions
1. Define work done. (2 marks)
Show the mark scheme answer
Product of force and displacement; in the direction of the force.
2. A motor lifts a 50 kg load through 12 m in 20 s. The electrical input power is 400 W. Calculate the efficiency. (3 marks)
Show the mark scheme answer
Gain in p.e. = 50 x 9.81 x 12 = 5886 J; useful power = 5886/20 = 294 W; efficiency = 294/400 = 0.74 or 74%.
3. A ball is released from rest 1.8 m above the ground. Ignoring air resistance, calculate its speed just before landing. (2 marks)
Show the mark scheme answer
mgh = 1/2 mv^2; v = square root of (2 x 9.81 x 1.8) = 5.9 m s-1.
1.8 Work Done, Potential and Kinetic Energy FAQs
What does CCEA A Level Physics 1.8 cover?
Work done, gravitational potential energy, kinetic energy, conservation of energy, power, efficiency and energy conservation in society.
Which unit is 1.8 examined in?
It is in Unit AS 1: Forces, Energy and Electricity.
What equations do I need for 1.8?
W = Fs, Δp.e. = mgΔh, k.e. = 1/2 mv^2, P = W/t (and P = Fv), and efficiency = useful output / total input.
