Energy of movement
Every moving object has a kinetic store. Greater mass or speed means more kinetic energy.
Lesson 1.3 · AQA Combined Science
Kinetic energy
Use the equation
Ek = ½mv²
| Symbol | Quantity | Unit |
|---|---|---|
| Eₖ | Kinetic energy | J |
| m | Mass | kg |
| v | Speed | m/s |
Square the speed first. v² means v × v, not v × 2.
Worked example
A 2 kg trolley moves at 3 m/s.
Ek = ½ × 2 × 3² = 9 J
Write the equation, substitute values, calculate and give the unit. Convert grams to kilograms before using the equation.
Challenge · changing mass and speed
At the same speed, doubling mass doubles kinetic energy. At the same mass, doubling speed makes kinetic energy four times larger.
To find mass: m = 2Eₖ / v². To find speed: v = √(2Eₖ / m).
Remember
Eₖ = ½mv². Use kg and m/s; square the speed before multiplying.
20 quick questions
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Question 1 of 20Spot · Match · Explain
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Read the numbers
How many particles?
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