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Mechanical Avantage

What is a machine?
A machine is a mechanical system that reduces the force required to accomplish work. Removing a lid from a can using your fingers is almost impossible since you cannot apply enough force. A can opener multiplies the amount of force that you can apply with your fingers in order to remove the lid. Another example would be a screw, you do not have enough force to put the screw into a wall with just by using your hands. A screw driver will multiply the force in order to put the screw in the wall.

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There are 3 different ways the machines make work easier.
1. by increasing the force that can be applied to an object
2. by increasing the distance over which the force is applied
3. by changing the direction of a force

Machines like a nutcracker and a ramp make work easier because the output force is greater than the input force. The amount by which a machine can multiply an input force is called mechanical advantage (MA).The ratio of the output force to the input force determines the machines mechanical advantage.

Mechanical Advantage of 1.
Not only can a machine multiply the input force and increase the distance over which the force is applied, but a machine can also change the direction of the force. An object that attaches to a rope that passes over a fixed pulley is a MA of 1 because the input and output force are the same size. If you pull down on the rope with force, the same amount of force is applied to the object. A fixed pulley is a machine that changes the direction of the force. Another example of a possible mechanical advantage equal to one is a class one lever.
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Input vs. Output forces
Formula: MA=Fout/Fin
mechanical advatage = output force/input force

Work Input: The total work a machine does.
Work Output: The work done by a machine that is useful.

Example: A force of 9N is exerted on a crowbar to pry open the lid on a box. The resultant force on the lid is 54N.
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What is the mechanical advantage?
MA= fout/fin
MA= 54N/9N
MA= 6