Q:

What is a first-class lever?

A:

Quick Answer

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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What is a first-class lever?
Credit: Joe Shlabotnik CC-BY-2.0

Full Answer

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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    A:

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