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First teaching 2014

Last exams 2024

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Kinetic Energy (DP IB Physics: SL)

Revision Note

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Kinetic Energy

  • Kinetic energy (Ek) is the 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 can be calculated using the following equation:

2-3-1-ib-sl-and-hl-ke-eqn-for-correcting

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 what is its new kinetic energy.

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

Examiner 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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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.