This topic summary covers Knowledge Organiser: Kinetic Energy within Kinetic Energy for GCSE Physics. Revise Kinetic Energy in Energy for GCSE Physics with 15 exam-style questions and 30 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 15 of 15 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Kinetic Energy
Key Terms
- Kinetic energy: energy stored in a moving object
- Mass: amount of matter, in kg
- Velocity: speed with direction, in m/s
- Work-energy theorem: work done = change in KE
Key Equation
- E_k = ½mv²
- Rearranged: m = 2E_k / v²
- Rearranged: v = √(2E_k / m)
- Units: J, kg, m/s
Key Facts
- KE ∝ mass (directly proportional)
- KE ∝ velocity² (squared relationship!)
- Double speed = 4× KE; triple speed = 9× KE
- KE transfers to thermal when object stops
Exam Tips
- Never forget the ½ or the squared on v
- Mass in kg, velocity in m/s — convert first
- Square root the result when finding v
- KE = GPE for falling objects problems
Common Mistakes
- Forgetting the ½: Eₖ = ½mv² — students often write mv², losing all marks on calculation questions
- Not squaring velocity: The v² means doubling speed quadruples KE — remember to square v before multiplying
- Wrong units: Mass must be in kg and velocity in m/s — convert before substituting
- Rearranging errors: To find v, divide by ½m first then square root — don't skip steps
- Confusing KE with momentum: KE = ½mv², momentum = mv — they are different quantities
Practice questions for Kinetic Energy
Which of the following objects has kinetic energy stored in its kinetic energy store?
A car travels at 20 m/s. The driver then doubles their speed to 40 m/s. Explain what happens to the kinetic energy of the car and by what factor it changes.
Quick recall flashcards
What is kinetic energy?
The energy stored in any object due to its motion. If it's moving, it has kinetic energy.
Kinetic energy equation?
Ek = ½mv² where m = mass (kg), v = velocity (m/s), Ek = kinetic energy (J)