12.3
Simple Machines12.3Inclined PlaneAn inclined plane is a flat,
sloped surface (ramp)An inclined plane allows you to exert your
input force over a long distanceThe input force needed is less than
the output forceThe input force used is the force with which you
push/pull an objectThe output force is the force you would need to
lift the object without an inclined planeTo determine the
mechanical advantage, you would divide the length of the incline by
the height
WedgeGive an example of a wedgeA wedge is a device that is thick
at one end and tapers to a thin edge at the other endInstead of
moving an object along the inclined plane, you move the inclined
plane itselfThe mechanical advantage can be determined by dividing
the length of the wedge by its width
ScrewsA screw can be thought of as an inclined plane wrapped
around a cylinder; the spiral inclined plane forms the threads of
the screwTwisting a screw into a piece of wood exerts an input
force on the screwThe threads of a screw act like an inclined plane
to increase the distance over which you exert the input
forceFriction between the screw and the wood holds the screw in
placeThe closer together the threads of a screw are, the greater
the mechanical advantageThe mechanical advantage can be found by
dividing the length around the threads by the length of the
screw
LeversGive an example of some leversA lever is a rigid bar that
is free to pivot, or rotate, on a fixed pointThe fixed point that a
lever pivots around is called the fulcrum3 classes of levers:1st
class-always change the direction of the input force; if fulcrum is
closer to the output force, the levers increase force; if fulcrum
is closer to input force, these levers increase distance; scissors,
pliers, seesaws2nd class-levers increase force, but do not change
the direction of the input force; doors, nutcrackers, bottle
openers3rd class-increase distance, but do not change the direction
of the input force; fishing poles, shovels, baseball bats
1st Class Levers2nd Class Levers3rd Class Levers
Wheel and AxleA wheel and axle is a simple machine made of two
circular or cylindrical objects fastened together that rotate about
a common axisThe object with the larger radius is the wheel and the
smaller radius is the axleThe wheel and axle increases your force,
but you must exert your force over a long distance
PulleyA pulley is a simple machine made of a grooved wheel with
a rope or cable wrapped around itYou use a pulley by pulling on one
end of the rope, which is the input force.The output force pulls up
on the object you want to moveTo move a heavy object over a
distance, a pulley can make work easier in 2 ways: it can decrease
the amount of input force needed to lift the object; the pulley can
change the direction of your input force2 basic types of pulleys:A
fixed pulley is one you attach to a structure (flagpoles)A movable
pulley is one you attach the object you wish to move (crane)Put a
fixed and movable pulley together and you get a block and
tackle
Compound MachinesA compound machine is a machine that utilizes 2
or more simple machines
