# Chapter 12 Work and Machines

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```					Chapter 12 Work and
Machines
Section 1 - What is work?
Work - The product of force and distance
when a force is used to move an object.
No work without motion

Work = Force x Distance
work units - Joules (J)

Problems pg 376
Chapter 12
Section 2 - Mechanical
Machine -
A device that changes the amount of force exerted or
the direction in which force is exerted.
A device with which you can do work in a way that
is easier or more effective.
A machine makes work easier by changing the
amount of force you exert, the distance over
which you exert your force, or the direction in
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Increase force, decrease distance
Increase distance, decrease force
force/input force
Efficiency = output work/input work x 100%

Chapter 12
Section 3 - Simple Machines
Six types of machines
Inclined plane
Wedge
Screw
Lever
Wheel & axle
Pulley

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Inclined Plane
Less force exerted over longer distance

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Wedge
Less force exerted over longer distance

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Screw
Inclined plane wrapped around a cylinder
Less force

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Lever
 Fulcum - the fixed point that a lever pivots around

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3 Types of Levers

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Wheel and Axle
Less force
exerted
over longer
distance
Doorknob

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Pulley
Change amount and direction of input force

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Section 4 - Machines in the
human body
Lifting levers - most of the machines in
your body are levers that consist of bones
and muscles.
Overhead -pg.401 Levers in the body
Wedges - front teeth (incisors)
Break toothpick in fingers

Chapter 12
Ch. 12 Vocabulary
work,                  wedge,
machine,               screw,
efficiency,            lever,
mechanical             fulcrum,
inclined plane,        pulley

Chapter 12

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