ASPhysicsCIERevision Notes5. Work, Energy & Power5.2 Energy: GPE & KE5.2.2 Kinetic Energy

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Kinetic Energy (CIE AS Physics)

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Derivation of KE = 1/2mv2

  • Kinetic energy is energy an object has due to its motion (or velocity)
  • 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

 

Kinetic Energy

  • Kinetic energy is energy an object has due to its motion (or velocity)
    • The faster an object is moving, 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 equation, downloadable AS & A Level Physics revision notes

Equation for Kinetic energy

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

KE: The energy an object has when its moving

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, what is its new kinetic energy?

WE - kinetic energy answer image, downloadable AS & A Level Physics revision notes

Examiner Tip

If a question asks about the ‘loss of kinetic energy’, don't be tempted to include a negative sign since energy is a scalar quantity.

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    Katie M

    Author: Katie M

    Expertise: Physics

    Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.