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.
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
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