Pearson Edexcel GCSE Combined Science · P3

Conservation of energy

Revision questions with answers for P3 Conservation of energy in Pearson Edexcel GCSE Combined Science (spec 1SC0). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

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Question 1 · Spec P3.5
Name eight energy stores.
Answer:
Kinetic, thermal, chemical, gravitational potential, elastic potential, nuclear, magnetic and electrostatic.
Question 2 · Spec P3.5
How do an energy store and a transfer pathway differ?
Answer:
A store describes where energy is held; a pathway describes how energy moves between stores.
Question 3 · Spec P3.5
Name four energy-transfer pathways.
Answer:
Mechanically, electrically, by heating and by radiation.
Question 4 · Spec P3.6
What is a closed energy system?
Answer:
A system considered without energy transfer to or from its surroundings.
Question 5 · Spec P3.6
What happens to total energy in a closed system?
Answer:
It stays constant, although energy can move between stores.
Question 6 · Spec P3.4
State conservation of energy.
Answer:
Energy cannot be created or destroyed, only transferred between stores.
Question 7 · Spec P3.5
Describe a thrown ball's energy changes as it rises.
Answer:
Its kinetic store decreases and gravitational potential store increases, with some energy dissipated if air resistance acts.
Question 8 · Spec P3.5
What energy change occurs as an object moves up a slope without friction?
Answer:
Kinetic energy is transferred into gravitational potential energy.
Question 9 · Spec P3.5
Where can a moving object's kinetic energy go when it hits an obstacle?
Answer:
Into deformation, thermal stores and sound, with possible movement of other objects.
Question 10 · Spec P3.5
What happens to the energy of an object accelerated by a force?
Answer:
Work done transfers energy into its kinetic store, with other transfers if resistance acts.
Question 11 · Spec P3.5
What happens to a braking vehicle's energy?
Answer:
Its kinetic store decreases while brakes and surroundings gain thermal energy.
Question 12 · Spec P3.5
Describe the main useful transfer in an electric kettle.
Answer:
Electrical transfer increases the water's thermal energy store.
Question 13 · Spec P3.1
State the change in gravitational potential energy equation.
Answer:
Change in GPE = mg x vertical height change.
Question 14 · Spec P3.1
Find GPE gain for 4 kg lifted 3 m, using g = 10 N/kg.
Answer:
4 × 10 × 3 = 120 J.
Question 15 · Spec P3.1
How does doubling mass affect GPE gain for the same height and g?
Answer:
It doubles the energy gain.
Question 16 · Spec P3.1
How does doubling vertical height affect GPE gain?
Answer:
It doubles the gain if mass and gravitational field strength stay constant.
Question 17 · Spec P3.1
Why must the local g value be considered in GPE calculations?
Answer:
The same mass and height change produce different energy changes in different gravitational fields.
Question 18 · Spec P3.2
State the kinetic-energy equation.
Answer:
KE = 0.5mv².
Question 19 · Spec P3.2
Find KE for 3 kg moving at 4 m/s.
Answer:
0.5 × 3 × 4² = 24 J.
Question 20 · Spec P3.2
How does doubling speed change kinetic energy?
Answer:
It quadruples KE at constant mass.
Question 21 · Spec P3.2
How does doubling mass change kinetic energy?
Answer:
It doubles KE at constant speed.
Question 22 · Spec P3.2
A 2 kg object has KE 100 J. Find speed.
Answer:
v² = 2 × 100/2 = 100; v = 10 m/s.
Question 23 · Spec P3.4
Ignoring air resistance, how does lost GPE compare with gained KE during a fall?
Answer:
They are equal, because mechanical energy is conserved.
Question 24 · Spec P3.3
What does arrow width represent on a Sankey diagram?
Answer:
The amount of energy transferred; outgoing widths sum to the input width.
Question 25 · Spec P3.3
A device receives 500 J and gives 350 J useful output. Find other energy transfers.
Answer:
500 − 350 = 150 J transferred in less useful ways.
Question 26 · Spec P3.8
What does energy dissipation mean?
Answer:
Energy spreads into less useful stores, usually thermal stores of the surroundings.
Question 27 · Spec P3.8
Why is dissipated energy harder to use?
Answer:
It is spread through the surroundings rather than concentrated in a useful store.
Question 28 · Spec P3.7
How can friction make a mechanical process wasteful?
Answer:
It transfers energy to thermal stores instead of the intended useful output.
Question 29 · Spec P3.9
How does lubrication reduce unwanted energy transfer?
Answer:
It reduces friction between moving surfaces, reducing unwanted heating.
Question 30 · Spec P3.9
Why does thermal insulation reduce energy waste from a hot object?
Answer:
It slows energy transfer to cooler surroundings.
Question 31 · Spec P3.10
How does higher wall thermal conductivity affect cooling?
Answer:
It increases the rate of energy transfer under otherwise comparable conditions.
Question 32 · Spec P3.10
How does greater wall thickness usually affect cooling?
Answer:
It reduces the rate of energy transfer through the wall.
Question 33 · Spec P3.10
How can insulation materials be compared fairly in a cooling experiment?
Answer:
Use equal thicknesses, containers, water amounts and starting temperatures, then compare temperature changes over equal times.
Question 34 · Spec P3.11
What does efficiency measure?
Answer:
The fraction of supplied energy transferred usefully.
Question 35 · Spec P3.11
State the efficiency equation.
Answer:
Efficiency = useful energy transferred / total energy supplied; multiply by 100 for a percentage.
Question 36 · Spec P3.11
A device gives 180 J useful output from 300 J input. Find efficiency.
Answer:
180/300 = 0.60 = 60%.
Question 37 · Spec P3.11
A 75%-efficient device receives 800 J. Find useful output.
Answer:
0.75 × 800 = 600 J.
Question 38 · Spec P3.11
A machine receives 1,000 J at 70% efficiency. Find dissipated energy.
Answer:
Useful = 700 J; dissipated = 1,000 − 700 = 300 J.
Question 39 · Spec P3.12 · Higher only
How could a motor's efficiency be improved?
Answer:
Reduce unwanted energy transfers, for example by reducing friction or electrical resistance.
Question 40 · Spec P3.13
What is a renewable energy source?
Answer:
A source replenished naturally or through managed replacement on a timescale comparable with use.
Question 41 · Spec P3.13
Name the principal non-renewable energy sources.
Answer:
Coal, oil, natural gas and nuclear fuel.
Question 42 · Spec P3.13
Name five renewable energy sources.
Answer:
Wind, sunlight, hydroelectricity, tides and biofuels.
Question 43 · Spec P3.13
Give a disadvantage of fossil-fuel electricity generation.
Answer:
It uses finite fuels and produces carbon dioxide and potentially other pollutants.
Question 44 · Spec P3.13
Give one benefit and one limitation of nuclear generation.
Answer:
Low operational carbon dioxide emissions, but finite fuel and radioactive waste management are concerns.
Question 45 · Spec P3.13
Why is wind generation variable?
Answer:
Wind speed changes, so output is not continuously controllable.
Question 46 · Spec P3.13
Why is solar output variable?
Answer:
It depends on daylight, season and weather conditions.
Question 47 · Spec P3.13
How can reservoir hydroelectricity help at peak demand?
Answer:
Water can be released rapidly to increase generation.
Question 48 · Spec P3.13
How does tidal power's predictability differ from continuous availability?
Answer:
Tidal cycles are predictable, but suitable generating conditions do not exist at every moment.
Question 49 · Spec P3.14
Why can energy-source use change over time?
Answer:
Technology, cost, demand, resource availability and environmental policies change.
Question 50 · Spec P3.14
What evidence should guide an energy-resource recommendation?
Answer:
Output, reliability, costs, environmental impacts and suitability for the required location and purpose.

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