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Work and Machines

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Arial Tahoma Calibri simple machines 1_simple machines Work and Machines PowerPoint Presentation PowerPoint Presentation Using Machines Effort and ... – PowerPoint PPT presentation

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Title: Work and Machines


1
Work and Machines
  • Work is the transfer of energy that occurs when
    a force makes an object move
  • For work to be done, a force must make something
    move
  • ex pushing on something that doesnt move is
    not doing work

2
  • Two conditions have to be met to do work on an
    object
  • 1. object has to move
  • 2. motion of the object must be in same
    direction as force applied
  • When work is done, a transfer of energy always
    occurs
  • So Energy is also the ability to do work (not
    just the ability to cause change)

3
  • Calculating Work
  • Work force X distance
  • OR
  • W F X d
  • Units for work are Joules
  • (Practice Calculating Work)

4
Using Machines
  • Machines a device that makes doing work easier
  • Machines increase the force applied to an
  • object OR increase the distance over which a
    force can be applied
  • Machines can also change the direction of an
    applied force
  • Ex car jacks, ramps, wedges

5
Effort and Resistance Forces
  • Two forces are involved when a machine is used to
    do work
  • Effort force the force applied to the machine
  • Resistance force the force applied by the
    machine to overcome resistance
  • Ex when you pull a nail out w/a hammer, effort
    force is applied to the handle, resistance force
    is applied to the nail by the claw

6
  • Efficiency a measure of how much of the work
    put into a machine is changed into useful output
    work by the machine
  • High efficiency means less heat produced from
    friction
  • Efficiency W output/W input X 100
  • Friction causes output work to always be less
    than the input work
  • SO Efficiency of a real machine is always less
    than 100
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