Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
Recall and use the equation to calculate the amounts of energy associated…
Full specification wording
Topic 3 – Conservation of energy: 3.2 Recall and use the equation to calculate the amounts of energy associated with a moving object: kinetic energy (joule, J) = 1/2 × mass (kilogram, kg) × (speed)² ((metre/second)², (m/s)²)
Kinetic energy is the energy a moving object stores because of its motion.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 2 of 10
Study notes
From the checked teaching notes for this specification point.
The idea
Kinetic energy is the energy a moving object stores because of its motion. The equation is E_k = ½ × m × v², where E_k is in joules (J), m is the mass in kilograms (kg) and v is the speed in metres per second (m/s). Because speed is squared, doubling the speed multiplies the kinetic energy by four, while doubling the mass only doubles it. Worked example: a 2 kg trolley moving at 3 m/s has E_k = ½ × 2 × 3² = ½ × 2 × 9 = 9 J. Convert grams to kilograms by dividing by 1000 before substituting, and square the speed before multiplying by the half and the mass. Rearranging gives m = 2E_k ÷ v² and v = √(2E_k ÷ m).
What earns the marks
- Squares the speed before multiplying by the half and the mass.
- Converts mass in grams to kilograms by dividing by 1000 before substitution.
- Substitutes values into E_k = ½ × m × v² and states the answer in joules.
- Rearranges the equation to find mass or speed when kinetic energy is given.
- Explains that doubling the speed quadruples the kinetic energy because speed is squared.
Common mistakes and how to put them right
Forgets to square the speed.
Put it right: Square the speed before multiplying.
Uses mass in grams instead of kilograms.
Put it right: Divide grams by 1000 first.
Multiplies by 2 instead of by ½.
Put it right: Apply the half factor to m × v².
Doubles the kinetic energy when speed doubles.
Put it right: Recognise that squaring the speed quadruples it.
Exam tips
- Write the equation, then substitute values with units before calculating.
- Check the unit of mass is kilograms and convert grams first.
- Square the speed as a separate step to avoid order-of-operations errors.
- Sanity-check the answer: a heavier or faster object must have more kinetic energy.
Try the lesson
The start of the Topic 3 – Conservation of energy: 3.2 Recall and use the equation to calculate the amounts of energy associated with a moving object: kinetic energy (joule, J) = 1/2 × mass (kilogram, kg) × (speed)² ((metre/second)², (m/s)²) lesson, made from checked teaching notes for this specification point.
Have a go first
A 2 kg trolley moves at a speed of 3 m/s. What is the kinetic energy of the trolley?
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Test your understanding of Topic 3 – Conservation of energy: 3.2 Recall and use the equation to calculate the amounts of energy associated with a moving object: kinetic energy (joule, J) = 1/2 × mass (kilogram, kg) × (speed)² ((metre/second)², (m/s)²)
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