Simple Machine: Levers

Simple machines are those devices that are used mechanically for the purpose of changing the direction or magnitude of a force. There are six different simple machines. They are - lever, wheel and axle, pulley, inclined plane, wedge and screw. All of them use some very simple mechanism that help to multiply the output force. In any simple machine, one single applied force is used to perform the task against the load force. If we ignore the loss of force that occurs due to friction, the amount of work done on the load is equivalent to the work done by the applied force. If we wish to increase the magnitude of the output force, there would be a proportional decrease in the length of the distance that is being moved by the load.

Lever - A Simple Machine

Lever has derived its name from the French word lever which means 'to raise'. The basic idea to make a lever work as a simple machine was developed by noted Greek philosopher Archimedes around third century BC. Even the perception of the mechanical advantage of the lever was made by him. A lever can be defined as a rigid object with a pivot point that is rightly positioned to enable it to increase the applied mechanical force on an object.

Working Principle

The working principle of the lever is based on Newton's laws of motion and modern theories of statics. We know that the total work done is a product of force and distance. A load is the physical object that is being lifted. A fulcrum in a lever is the thing that helps in making the load lighter. An effort is the person who pushes or pulls to move the object. The distance between the fulcrum and point of effort is called 'effort arm' and that between fulcrum and the load is called 'load arm'. Thus the Law of the Lever can be defined by the formula: (Load arm) × (Load force) = (Effort arm) × (Effort force)

Classes

Levers are categorized into three different classes. This classification is based on the variations in the position of the fulcrum and the resultant input and output forces.

First-Class - In this kind of lever, the fulcrum is positioned anywhere between the input effort and the output load. Here, the fulcrum supports the effort arm. When a force, a push or pull, is given to a portion of the bar, it makes the lever swing about the fulcrum and help to overcome the opposite force. For example - seesaw or teeter-totter.

Second-Class - The fulcrum of a second class lever is located at one end while the input effort is at the other end of the bar. It means the fulcrum and the input is opposite to each other and the output load lies at a point in between these two forces. For example - diving board or spring board.

Third-Class - In a third class lever, the output load and the fulcrum are at the opposite ends and the input effort is applied between these two. This type of lever is different from the other two because its input effort is higher than the output load. However, the distance covered by the load is more in comparison to the distance of the effort. As a result, the load moves faster than the effort. For example - a fishing rod. Here, the handle of the rod is the fulcrum and the fish is the output load.

"Give me a lever long enough and a fulcrum on which to place it, and I shall move the world" - Archimedes. Hence, we can say that the lever is one such tool which is capable of changing the distance and power of movement.