P1: Conservation and Dissipation of Energy

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  • Created by: Annie3467
  • Created on: 15-05-17 16:27

P1.1 and P1.2 Changes in Energy Stores + Conservat

P1.1

  • Energy can be stored in a variety of different energy stores
  • Energy is transferred by heating, by waves, by an electric current, or by a force when it moves an object
  • When an object falls and gains speed, its store of GPE decreases and its kinetic energy store increases.
  • When a falling object hits the ground without bouncing back, it's kinetic energy store decreases. Some or all of its energy is transferred t the surroundings - the thermal energy store of the surroundings increases, and energy is also transferred by soundwaves.

P1.2

  • Energy cannot be created or destroyed.
  • Conservation of energy applies to all energy changes.
  • A closed system is a system whch no energy transfers take place out of or into the energy stores of the system
  • Energy can be transferred between energy stores within a closed system. The total energy of the system is always the same, before and after, any such transfers.
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P1.3 and P1.4 Energy and Work + GPE stores

P1.3

  • Work is done on an object when a force makes the object move. 
  • Energy Transferred = Work Done
  • Work done, W (joules, J) = Force applied, F (newtons, N) x distance moved along the line of action of the force, s (metres, m)
  • Work done to overcome friction is transferred as energy to the thermal energy stores of the objects that rub together and to the surroundings. 

P1.4

  • The GPE store of an object increases when it moves up and decreases when it moves down.
  • The gravitational potential energy store of an object increases when it is lifted up because work is done on it to overcome the gravitational force.
  • The gravitational field strength on the moon is less than on the earth. 
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P1.5 Kinetic energy + elastic energy stores

P1.5

  • The energy in the kinetic energy store of a moving object depends on its mass and its speed.
  • The kinetic energy store of an object is Kinetic Energy = 1/2 x mass x speed^2
  • Elastic Potential energy is the energy stored in an elastic object when work is done on the object.
  • The elastic potential energy stored in a stretched spring is Elastic Potential energy = 1/2 x spring constant x extension^2
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