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SIMPLE MACHINES
THE LEVER FAMILY
simple machines
 One of six basic types of machines which are basis for all
other forms of machines.
 have a rigid arm and a fulcrum.
six types divided into two families.
lever family:
inclined plane family:
simple lever
(3 types)
pulley


wheel and axle

simple inclined plane

wedge

screw
FIRST CLASS LEVERS
 fulcrum located between points of application
of input and output forces.
 seesaw
SECOND CLASS LEVERS
• fulcrum is at one end of arm and input force is
applied to other end.
• wheelbarrow
THIRD CLASS LEVERS
•
•
•
multiply distance rather than force.
have a mechanical advantage of less than 1.
arm
PULLEYS
 modified
levers.
 point in middle of a pulley is like fulcrum
of a lever.
 single, fixed pulley has a m. a. of 1.
block and tackle:
 Multiple pulleys working together
PULLEYS
WHEEL & AXLE
 a lever or pulley connected to a shaft.
 steering wheel of a car, screwdrivers, and cranks
THE INCLINED PLANE FAMILY
 multiply and redirect force.
 turns small input force into large output
force by spreading work out over a large
distance.
SIMPLE INCLINED PLANE
 Changes both magnitude & direction of force
WEDGE
 Functions as two inclined planes back to back.
 Turns single downward force into two forces directed
out to sides.
SCREW
 an inclined plane wrapped around a cylinder.
Chapter 12
COMPOUND MACHINES
 machine made of more than one
simple machine
Examples :
scissors
• two first class levers joined at a
common fulcrum
car jack
• combination of lever with a large
screw