There are three classes of levers: Class 1, class 2, and class 3. They all have different mechanical advantages. Class 1 levers can have mechanical advantage of 1, less than 1, or more than 1. Class 2 levers always have a mechanical advantage of more than 1; and class 3 levers always have a mechanical advantage of less than 1.
Class 1
Class 1 levers always have the fulcrum in between the load arm and the effort arm. The input force is always going in the opposite direction of the output force. The mechanical advantage can be anything. This is because the load arm can be longer than the effort arm and the effort arm could be longer than the load arm. Also remember that the weight of the load will affect the mechanical advantage. For example if you have a load arm and an effort arm equal in length. The mechanical advantage can still be less than 1 if the load arm has a heavy weight. An example of a class 1 lever is a teeter totter.
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Class 2
Class 2 levers always have the fulcrum at the end of the lever opposite where the input force is applied. In a class 2 lever the output force and input force are always going in the same direction. In a class 2 lever the mechanical advantage is always more than 1. This is because the effort arm is always longer than the load arm. Two examples of class 2 levers are a wheel barrow and a crowbar.
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Class 3
The class 3 lever has the input force between the output force and the fulcrum. A class 3 lever is useful for generating speed at the output end of the lever. It generates speed because the output end has to travel a longer distance in a shorter time compared to the input end. Just like a class 1 lever, the input force and the output force are always going in the opposite direction. The mechanical advantage of a class 3 lever is always less than 1 because the load arm is always longer than the effort arm. Two examples of a class 3 lever are a hockey stick and a rake.
Class 1
Class 1 levers always have the fulcrum in between the load arm and the effort arm. The input force is always going in the opposite direction of the output force. The mechanical advantage can be anything. This is because the load arm can be longer than the effort arm and the effort arm could be longer than the load arm. Also remember that the weight of the load will affect the mechanical advantage. For example if you have a load arm and an effort arm equal in length. The mechanical advantage can still be less than 1 if the load arm has a heavy weight. An example of a class 1 lever is a teeter totter.
Class 2
Class 2 levers always have the fulcrum at the end of the lever opposite where the input force is applied. In a class 2 lever the output force and input force are always going in the same direction. In a class 2 lever the mechanical advantage is always more than 1. This is because the effort arm is always longer than the load arm. Two examples of class 2 levers are a wheel barrow and a crowbar.
Class 3
The class 3 lever has the input force between the output force and the fulcrum. A class 3 lever is useful for generating speed at the output end of the lever. It generates speed because the output end has to travel a longer distance in a shorter time compared to the input end. Just like a class 1 lever, the input force and the output force are always going in the opposite direction. The mechanical advantage of a class 3 lever is always less than 1 because the load arm is always longer than the effort arm. Two examples of a class 3 lever are a hockey stick and a rake.
Links
Intro
Load Arm and Effort Arm
Levers and Friction
Classes Of Levers
Human Levers
Wheels
Bibliography