# Work and Machines - PowerPoint PPT Presentation

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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