THIRD-CLASS LEVERS

• A third-class lever has the input force between the fulcrum and output force.
• The output and input force are always in the same direction.
• A third-class lever is useful because the speed and distance of the output end of the lever are greater then at the input end.
• A third class lever always produces a mechanical advantage less than because the output force is alwaysless than the input force.

Class 3 Lever

The effort arm is between the effort and the fulcrum:

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The load/resistance arm is between the effort and the load/resistance:




The farther away you move the effort the less force you need to lift the load.

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Ideal Mechanical Advantage: the mechanical advantage of a machine that has no friction

IMA =L in / L out

L in: Length of the input arm

L out: Length of the output arm

The length of the load/output arm is always less than the length of the effort/input arm.

∴Therefore the Ideal mechanical advantage of a third-class lever is always less than 1.

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Examples of third-class levers :

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Tennis Racket

Baseball Bat

Catapult

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