Mechanical advantage (also written asMA in formulas) is the factor by which amachine multipliesforce. The mechanical advantage of a machine can be used to find out how well a machine works and whether it can perform a particular job.
The mechanical advantage of a machine is the ratio of the load (the resistance overcome by a machine) to the effort (the force applied).
For an ideal (withoutfriction) mechanism, it is also equal to:
There are two types of mechanical advantage: ideal and actual.
Ideal mechanical advantage (also written as IMA) assumes that nopower is lost byfriction or other causes. This means the power of the input (load) should equal the power of the output (effort). So, force timesspeed of the input should equal force times speed of the output.
You can calculate ideal mechanical advantage without measuring the forces. It is the distance over which effort is applied, divided by the distance over which the load is moved.
In reality, there is friction, so some of the power is lost. Theactual mechanical advantage (also written as AMA) is always less than ideal. To calculate actual mechanical advantage, you must measure the forces. Then divide the output force by the input force.
Themechanical efficiency is the ratio of the actual mechanical advantage to the ideal mechanical advantage. It is also written as η, the Greek lettereta.
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See the illustration. In the top picture of the right column, a lever isdelivering a force to a stone. If there is amechanical advantage of2, then theoutput force is twice the size of theinput force.
There is no unit for mechanical advantages, because the unit for both input and outputforces cancel out.
