The lever is a basic part of how things work in mechanics. It's like a sturdy stick or rod that can move around a fixed point called the fulcrum. This simple tool is really useful and can help us do lots of things more easily.

When we talk about "leverage," we mean how the lever makes things easier. By using a lever, we can make a small force do a bigger job. Scientists long ago saw the lever as one of the six simple machines because it's so important in making machines work.

In everyday life, a lever helps us get things done by letting us use less force over a longer distance to make stuff happen. Because of the way it's built, a lever can make tasks easier and quicker. Whether it's building something, making things in a factory, or just doing chores around the house, the lever helps us get the job done better.

So, the next time you use a lever, remember how it's a simple tool that makes big tasks easier by giving us a mechanical advantage and making our efforts more effective.

History of the Lever

The lever, one of the fundamental principles of mechanics, has a rich history dating back to ancient civilizations. From its early origins to its integral role in modern engineering and technology, the lever has been a cornerstone of human innovation and progress.

Throughout history, the lever has exemplified the principles of simplicity, efficiency, and versatility. Its ability to amplify force and motion has enabled humans to overcome physical limitations and accomplish tasks of immense complexity. As a timeless symbol of ingenuity and innovation, the lever continues to shape the course of human progress in the twenty-first century and beyond.

Mechanical Advantage (MA)

A lever is a beam connected to ground by a hinge, or pivot, called a fulcrum. The ideal lever does not dissipate or store energy, which means there is no friction in the hinge or bending in the beam. In this case, the power into the lever equals the power out, and the ratio of output to input force is given by the ratio of the distances from the fulcrum to the points of application of these forces. This is known as the law of the lever. The mechanical advantage of a lever can be determined by considering the balance of moments or torque, T, about the fulcrum. If the distance traveled is greater, then the output force is lessened. The mechanical advantage of the lever is the ratio of output force to input force. 

This relationship shows that the mechanical advantage can be computed from ratio of the distances from the fulcrum to where the input and output forces are applied to the lever, assuming no losses due to friction, flexibility or wear. This remains true even though the "horizontal" distance (perpendicular to the pull of gravity) of both a and b change (diminish) as the lever changes to any position away from the horizontal.

Classes of Levers and Common Uses

The lever is classified into three main types based on the relative positions of the fulcrum, load, and effort. In a first-class lever, the fulcrum lies between the load and the effort, such as in a seesaw or crowbar. Second-class levers have the load between the fulcrum and the effort, as seen in a wheelbarrow or a bottle opener. Third-class levers position the effort between the fulcrum and the load, commonly found in tools like tweezers or fishing rods.

Class I

Fulcrum between the effort and resistance: The effort is applied on one side of the fulcrum and the resistance (or load) on the other side, for example, a seesaw, a crowbar, or a pair of scissors, a common balance, a claw hammer. Mechanical advantage may be greater than, less than, or equal to 1.

Class II

Resistance (or load) between the effort and fulcrum: The effort is applied on one side of the resistance and the fulcrum is located on the other side, e.g. in a wheelbarrow, a nutcracker, a bottle opener or the brake pedal of a car, the load arm is smaller than the effort arm, and the mechanical advantage is always greater than one. It is also called force multiplier lever.

Class III

Effort between the fulcrum and resistance: The resistance (or load) is on one side of the effort and the fulcrum is located on the other side, for example, a pair of tweezers, a hammer, a pair of tongs, fishing rod or the mandible of a human skull. The effort arm is smaller than the load arm. Mechanical advantage is always less than 1. It is also called speed multiplier lever.