• Created by: ak27330
  • Created on: 05-01-20 16:13
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  • P8
    • Energy Transfers and Systems
      • system change, energy transferred. Closed system- net change in energy is 0
      • some energy dissipates, efficiency is the proportion of the total energy supplied that ends up in useful stores
      • Energy is transferred mechanically when work is done by or against a force
      • Heating transfer from thermal of hot object to thermal of cold
    • Work Done
      • Work done is the energy transferred when a force acts on an object
      • When something moves, effort is needed
      • E = F x d
        • E = work done(J)       F= Force(N) d= distance(m)
      • ?GPE = mg x ?h
      • KE = 0.5 x mv²
    • Dissipation of Energy
      • Some energy dissipates to thermal energy of a moving object
      • Push something along a rough surface, work against frictional forces
        • Transferred to kinetic store, some to thermal due to friction. Increases temp
      • Lubricants can be used to reduce friction between objects
      • efficiency= useful energy/ total energy
    • Power
      • rate of energy transfer, or the rate of doing work
      • P=E/t
        • P - power(w) E - work done(J) t -time(s)
      • Powerful machine, transfers lots of energy quickly


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