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How Tools Work
The Six Simple Machines
Lever
Inclined Plane
Wedge
Screw
Pulley
Wheel and Axle
Lever
A bar that pivots on a fulcrum—a fixed point
Levers apply force to a load
Three classes, depending on placement of fulcrum, load, and input force
Inclined Plane
A straight, slanted surface Ex: a ramp
Requires less input force than going straight up
***does NOT reduce work (W= f x d)
Wedge Two inclined planes
that move Often used for
cutting You a knife down as
it cuts apart
The sharper the wedge, the greater output force for your input force
Screw An inclined plane
wrapped in a spiral around a cylinder Usually used as
fasteners
Smaller force over a longer distance The small force of
you turning pushes the screw along its spiraled threads
Pulley A grooved wheel
that holds a rope or cable
A load is attached to one end of the rope, and the input force is applied to the other end
Wheel and Axle Two circular objects of
different sizes used to create a larger output force
Turn the larger circle around a longer distance as the smaller circle, traveling a shorter distance, creates a larger output force
The larger the wheel, the less force needed to move the load
Compound Machines
A machine made up of two or more simple machines
Most machines in the world, including how your body works, are compound
Mechanical Advantage How many times a
machine multiplies force
Mechanical Advantage is calculated by dividing the output force by the input force MA= out/in
If MA > 1, the machine helps lift heavy objects
If MA < 1, the machine increases the distance and reduces the output force
Name that Machine!