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Machines

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Machines Ch 5 Sect 2 Machine Device that makes doing work easier Machines do not have to be complicated Machines can work in 3 different ways Ways Machines Work ... – PowerPoint PPT presentation

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Title: Machines


1
Machines
  • Ch 5 Sect 2

2
Machine
  • Device that makes doing work easier
  • Machines do not have to be complicated
  • Machines can work in 3 different ways

3
Ways Machines Work
  • Increase amount of force being applied
  • Use a machine to increase leverage which makes
    doing work seem easier

4
Ways Machines Work
  • 2. Increase distance
  • By increasing distance you use a smaller amount
    of force over a longer distance
  • moving van

5
Ways Machines Work
  • Changing Direction
  • chopping wood

6
Forces and Machines
  • Effort force is the force that is applied to the
    machine (you apply force)
  • Represented by Fe
  • Resistance force is the force applied by the
    machine to over come resistance (machine applies
    force)
  • Represented by Fr
  • Machine can move obj. that resist motion

7
Forces and Work
  • Effort force is transformed to input work
  • Input work is done by you (w-in)
  • Resistance force is transformed to output work
  • Output work is done by the machine (w-out)
  • nail removal

8
Machines and Energy
  • Machines work based on the transfer of energy
  • You transfer energy to the machine
  • The machine then transfers the energy to the
    object being worked on

9
Machines and the Law of Conservation of Energy
  • Conservation of energy states that energy can
    never be created or destroyed, therefore the
    machine can never create extra energy
  • Machine can never give more energy then it
    receives
  • w-out can never be greater then w-in

10
Ideal Machines
  • An ideal machine is a machine in which all input
    work is transferred to useable output work
  • w-in w-out
  • No work/energy would be wasted

11
Efficiency
  • Measure of how much work put in to a machine is
    changed to useable out put work
  • Efficiency can never be more than 100
  • Humans are about 30-35 efficient
  • Gas powered cars are about 7-12 efficient
  • Increase efficiency by decreasing friction

12
Calculating Efficiency
  • Work out / work in x 100
  • Out put work is always less then input work so
    efficiency will be less then 100

13
Mechanical Advantage (MA)
  • The number of times a machine multiplies the
    effort force
  • To find MA you divide Fr by Fe
  • MAFr/Fe
  • If you are only changing the direction of the
    force MA always equals one
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