Simple Machines
There are six basic kinds of simple machines: inclined plane, pulley, wheel and axle, screw, and lever.
Inclined Plane
A flat, sloped surface.
How It Works
An inclined plane lets you exert your input force over a longer distance.
As a result the input force needed is less than the output force.
Mechanical Advantage
divide the length by its height
Ideal MA = length / height
Wedge
A device that is thick at one end and tapers to a thin edge at the other end.
How It Works
You move the inclined plane itself.
Mechanical Advantage
Divide the length by its width.
Ideal MA = length / width
Screws
An inclined plane wrapped around a cylinder.
How It Works
The threads of a screw act like an inclined plane.
As the threads of a screw turn, they exert an output force on the object, pulling the screw into the object.
Friction between the screw and the wood holds the wood in place.
Mechanical Advantage
Length around the threads divided by the length of the screw.
Levers
A rigid bar that is free to pivot, or rotate, on a fixed point called the fulcrum.
How It Works
When you use push down the lever pivots lifting the other end/the load.
Mechanical Advantage
Divide the distance from the fulcrum tot he input force by the distance from the fulcrum to the output force.
Ideal mechanical advantage = distance form fulcrum to input force / distance from fulcrum to output force
Levers are classified according to the location of the fulcrum relative to the input and output force.
Wheel and Axle
Made of two circular or cylindrical objects fastened together that rotate about a common axis.
How It Works
Because the wheel is larger than the shaft, or axle, the axle rotates and exerts a large output force. the wheel and axle increases your force, but you must exert your force over a long distance.
Mechanical Advantage
Divide the radius of the wheel by the radius of the axle.
Pulley
Made of a grooved wheel with a rope or cable wrapped around it.
How It Works
You use input force to pull on one end of the pulley so that way the other end move upward which is the output force.
A pulley can decrease the amount of input force used to lift an object.
A pulley can change the direction of your input force.
Simple Machines in the Body
Mechanical Advantage
The number of sections of rope that support the object.
Living Levers
Most of the machines in your body are levers that consist of bones and muscles.
Tendons and muscles pull on bones, making them works as levers.
Joints act as fulcrums.
The muscles produce the input force.
Working Wedges
Incisors are an example of a wedge.
Compound Machines
Two or more simple machines.
Mechanical Advantage
The product of the ideal mechanical advantages of the simple machines that make it up.