Work, energy and momentum

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  • Created by: Holly45
  • Created on: 18-03-15 17:47

Car safety

  • brakes do work against the kinetic energy of the car
  • the brakes reduce the kinetic energy of the car by transferring heat and sound energy
  • cars are designed to convert kinetic energy safely in a crash
  • if a car crashes it will slow down very quickly, this will mean that a lot of kinetic energy is converted into other forms of energy in a short time, which can be dangerous


  • stretch slightly increasing the time taken for the wearer to stop
  • this reduces the forces acting on the chest
  • kinetic energy is absorbed by the seat belt


  • slow you down gradually and prevent you from hitting hard surfaces inside the car
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Momentum and collision

  • momentum = mass X velocity
  • momentum is the property of moving objects
  • the greater the mass of an object and the greater its velocity the more momentum the object has
  • momentum has size and direction
  • momentum before = momentum after
  • forces can cause changes in momentum
  • a larger force means a faster change in momentum
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Forces and elasticity

  • work done to an elastic object is stored as elastic potential energy
  • any object that can go back to its original shape after the force has been removed is an elastic object
  • elastic potential energy is converted into kinetic energy when it returns to its original shape
  • extension of a stretched spring is directly proportional to the force applied
  • F = K x E (where K is the spring constant)
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Work and potential energy

  • when a force moves an object through a distance, energy is transferred and work it done
  • work done = force X distance
  • gravitational potential energy = mass X g X height
  • gravitational potential energy is the energy that an object has by virtue because of its vertical position on a gravitational field
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Kinetic energy

  • energy of movement
  • kinetic energy = 1/2 X mass X speed squared
  • kinetic energy transferred is work done
  • it needs to be converted into heat energy as friction between the wheels and brake pads
  • kinetic energy transferred = work done by brakes
  • kinetic energy gained = potential energy lost
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