Credit: Joe Shlabotnik CC-BY-2.0
Q:

# What is a first-class lever?

A:

A first-class lever is a beam, rod or stick with the load at one end, the fulcrum in the middle and the force applied on the other end. A good example of a first-class lever is a child's see-saw.

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Levers are simple machines — apparatuses composed of few or no moving parts that make performing a task easier by one or more of four methods:

• Transferring where the force is applied to where it acts
• Changing the distance over which the force is applied or the speed with which it is applied
• Changing the direction of the applied force to that of the acting force
• Increasing the magnitude of the acting force over that of the applied force

There are three classes of levers, based on the arrangement of the load, the fulcrum and the location where the force is applied:
• First-class: fulcrum between the force and the load. Examples include a crowbar and a balance scale.
• Second-class: load between the force and the fulcrum. Examples include a wheelbarrow.
• Third-class: force between the load and the fulcrum. Examples include hammers and catapults.

A first-class lever makes a task easier by two methods:

• It changes the direction of the force. The force pushes down on one end of the lever, causing the load on the other end to rise.
• It changes the distance over which the force is applied in exchange for how much force must be applied. When the point where the force is applied is moved farther away from the fulcrum, the force needed to push the lever down decreases; however, the distance that it must be pushed increases.

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## Related Questions

• A:

Examples of first-class levers include a balance scale, a seesaw and a crowbar. A first-class lever places the fulcrum in the middle of the effort and the load.

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• A:

Some of the types of first-class levers include crowbars, scissors, seesaws, fishing rods, pliers, balance scales, trebuchets and hammers when removing nails. All of these levers have a fulcrum positioned between load and effort. First-class levers are the most common type of levers.

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• A:

A uniformly distributed load has a constant value, for example, 1kN/m; hence the "uniform" distribution of the load. Each uniformly distributed load can be changed to a simple point force that can be used to determine the stresses in an object.