# Machines - PowerPoint PPT Presentation

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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
• 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