Levers of first order
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The distance AF is called the effort arm and the distance BF is called the load arm.
If the lever is in equilibrium, then by applying the principle of moments about the fulcrum, we get
Clockwise moment = Anticlockwise moment
Effort x Effort arm = Load x Load arm
The ratio of the effort to the load is the mechanical advantage of the lever, therefore
Depending upon the relative position of load, fulcrum and effort, the mechanical advantage (shown in figure below) of the class I lever may be any of the following:
Relative positions of load, fulcrum and effort of class I lever
when Load arm = Effort arm, e.g. beam balance
when Effort arm > Load arm, e.g. Cutting pliers
when Effort arm < Load arm, e.g. Garden scissors
Equal Arms Beam Balance
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A beam balance is an example of the class I type of levers (Shown figure below).
Beam Balance
It consists of two arms of equal lengths and two pans of equal weights. It works on the principle of moments. The turning effect produced by the mass on the left pan is equal to the turning effect produced by the pan on the right. Thus, if standardized weights are used in one of the pans the weight in the other pan can be known.
A true balance remains in equilibrium when either equal weights are put in both the pans or equal weights are removed from both the pans.
