Work and Energy (G481)

Work and Energy mindmap, the first half of Module 3:

  • Work 
  • Power
  • Potential energy
  • Kinetic energy
  • Conservation of energy 
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  • Created by: Anna
  • Created on: 08-04-13 12:51
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  • Work and Energy
    • Work and Power
      • Work done is the "product of the force and the distance moved by the force in the direction of travel"
        • W=Fx
          • F measured in Newtons (N)
          • W measured in Joules (J)
          • x is measured in meters (m)
            • Remember to convert from cm/km/mm etc
        • W=Fxcos?
          • You can use a force triangle to work out these kinds of questions
          • This is because it must be the distance moved IN THE DIRECTION OF THE FORCE
        • Work done = Energy transferred
          • E.g. moving a  book from a low shelf to higher one increases it's GPE but it had some to begin with so work done is the increase in GPE NOT the total
      • Power is the "rate at which energy is transferred or the rate at which work is done
        • P=W/t
          • P is measured in Watts (W)
            • "Watt is the unit of Power"
          • W is work done - do not confuse with Watts (W)!
          • t measured in s
          • P=Fv
            • W = Fx so P = Fx/t and v=x/t hence P = Fv
    • Conservation of Energy
      • "Energy cannot be created or destroyed. Energy can be transferred from one form to another but the total amount of energy in a closed system will not change."
      • Because of this the kinetic energy transferred to gravitational must be equal and the other way around
        • GPE = KE
          • 1/2mv^2=mgh
            • m's cancel out
              • 1/2v^2=gh
                • v^2=2gh
          • KE = 1/2mv^2
            • KE measured in Joules (J)
            • m measured in kilograms (Kg)
            • v measure in meters per second (ms^-1)
    • Kinetic Engery
      • Kinetic Energy is the "energy of an object due to its motion"
        • KE = 1/2mv^2
          • KE measured in Joules (J)
          • m measured in kilograms (Kg)
          • v measure in meters per second (ms^-1)
    • Potential Energy
      • elastic potential energy
        • Energy stored in an extended or compressed material
          • E = 1/2 ke^2
            • e is the extension and is measured in m
            • k is the stiffness constant
            • E is  measured in Joules (J)
      • gravitational potential energy
        • "Energy stored by an object by virtue of its position in the Earth's gravitational field."
        • GPE = mgh
          • GPE measured in Joules (J)
            • The Joule is defined by the work done when 1N moves an object by 1m which can be seen by looking at the units of equations. Here we have a mass, an acceleration and distance. F=ma so we have the equivalent.
          • g measured in ms^-2 (acceleration due to gravity/ free fall and is = 9.81)
            • The Joule is defined by the work done when 1N moves an object by 1m which can be seen by looking at the units of equations. Here we have a mass, an acceleration and distance. F=ma so we have the equivalent.
          • these can be combined, see "conservation of energy.

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