Kinetic Energy (Edexcel A Level Physics)

Revision Note

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Lindsay Gilmour



Kinetic Energy

  • Kinetic energy (usually written Ek and sometimes KE) is the energy an object has due to its motion (or velocity)
    • The faster an object moves, the greater its kinetic energy

  • When an object is falling, it is gaining kinetic energy since it is gaining speed
    • This energy transferred from the gravitational potential energy it is losing
    • An object will maintain this kinetic energy unless its speed changes

  • Kinetic energy can be calculated using the following equation:


Kinetic energy diagram, downloadable AS & A Level Physics revision notes

Kinetic energy (KE): The energy an object has when it is moving

Derivation of Kinetic Energy Equation

  • A force can make an object accelerate; work is done by the force and energy is transferred to the object
  • Using this concept of work done and an equation of motion, the extra work done due to an object's speed can be derived
  • The derivation for this equation is shown below:

Derivation of KE = 1_2mv2, downloadable AS & A Level Physics revision notes

Worked example

A body travelling with a speed of 12 m s–1 has kinetic energy 1650 J.

If the speed of the body is increased to 45 m s–1, estimate its new kinetic energy.


Exam Tip

When using the kinetic energy equation, note that only the speed is squared, not the mass or the ½.

If a question asks about the ‘loss of kinetic energy’, remember not to include a negative sign since energy is a scalar quantity.

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Lindsay Gilmour

Author: Lindsay Gilmour

Lindsay graduated with First Class Honours from the University of Greenwich and earned her Science Communication MSc at Imperial College London. Now with many years’ experience as a Head of Physics and Examiner for A Level and IGCSE Physics (and Biology!), her love of communicating, educating and Physics has brought her to Save My Exams where she hopes to help as many students as possible on their next steps.

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