Students apply the law of conservation of energy to account for every joule in a device, then calculate efficiency as a percentage using energy and power, rearranging the formula to find useful output or total input. They analyse energy flow (Sankey) data, use gravitational potential energy (mgh) and kinetic energy (½mv²) to solve conservation problems for falling objects, roller coasters, bouncing balls and lifts, and explain how efficiency can be improved.
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Curriculum: Australian Curriculum. We show specific outcome codes only where they have been verified against the official curriculum document.
Completed: Conservation of Energy and Efficiency Calculations
Year 10 students (typically ages 15–16) working on energy, light, sound & electricity. It is pitched at level 3 · challenge.
Yes. The PDF includes a full answer sheet with model answers and success criteria where there is more than one good answer. You can also view the answers online.
About 45 minutes for 20 questions. Short, regular sessions work best: two or three a week beats one long one.
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Try Electrical Power, Energy and the Cost of Electricity.
Success TutoringWorksheetsYear 10 · Science · Energy, Light, Sound & ElectricityName
Date
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Efficiency = useful output ÷ total input × 100%. Total input = useful output + wasted energy.
Show the formula, your working and units. Give efficiencies as percentages.
The law of conservation of energy: energy cannot be created or destroyed, only transferred or transformed. The total energy before a change equals the total energy after it.
In any device, the total energy input = useful energy output + wasted energy. Wasted energy is usually thermal energy (and sometimes sound) that spreads out into the surroundings, where it is hard to use again.
Efficiency = useful energy output ÷ total energy input × 100%. It can also be calculated with power (in watts) in place of energy. Rearranged: useful output = efficiency × total input and total input = useful output ÷ efficiency, with the efficiency written as a decimal (for example 75% = 0.75).
Gravitational potential energy: Ep = mgh, where m is mass (kg), g = 9.8 N/kg on Earth and h is height (m).
Kinetic energy: Ek = ½mv[sup 2], where v is speed (m/s). Energy is measured in joules (J).
When an object falls with no air resistance, all of the potential energy it loses becomes kinetic energy. In real situations some energy is transferred to the surroundings as thermal energy and sound.
Preview — the PDF contains the full resource and answer sheet.
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