Levers are simple machines designed to make work easier by reducing human effort. A simple machine is a device that changes the magnitude or direction of a force, allowing tasks to be performed more efficiently. Levers help us lift or move heavy objects by improving the applied force, a property known as leverage.
A lever consists of a rigid bar or beam that rotates about a fixed point called the fulcrum. By adjusting the positions of the applied force and the load, a lever can amplify or redirect force, making difficult tasks easier. In some cases, levers are also used to increase speed or distance of movement rather than force.
What is Lever?
A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load, and effort, the lever is divided into three types.
It is one of the six simple machines identified by Renaissance scientists. A lever amplifies an input force to provide a greater output force, which is said to provide leverage, which is mechanical advantage gained in the system, equal to the ratio of the output force to the input force.
As such, the lever is a mechanical advantage device, trading off force against movement.
Parts of a Lever
A lever system consists of four parts – beam, fulcrum, load, and effort.
- Beam: A plank made out of wood or metal.
- Fulcrum: The pivot point about which the beam rests and moves freely. Since the beam can move freely, the fulcrum is also known as the lever’s turning point.
- Load (L): Load is a resistive force that has to be overpowered by simple machines. The S.I. unit of load is Newton (N).
- Effort (E): Effort is the external force used to pull off a load on a simple machine. The S.I. unit of effort is the Newton (N).
- Pivot: It refers to the support provided at a specific point.
- Mechanical Advantage (MA): It is the ratio of the effort arm to the load arm. It is given as MA = Effort Arm (E)/Load Arm (L).
- Effort Arm: The distance between the effort (force) and the Fulcrum (pivot)
- Load Arm: The distance between the Load and the Fulcrum (pivot).
Principle of Lever
Various experiments show that there are two equal forces which are found acting in opposite directions to each other, which are clockwise and in anti- clockwise direction, and are thus applied in a uniform lever at an equal distance from the fulcrum, counteracting each other so that a state of equilibrium, or balance, in the lever is established.
It has been shown that there are found to be two unequal forces which are found acting in opposite directions. This is responsible for bringing the magnitude of a force whenever the magnitude is found to be in one force. The effort made by the arm or lever arm is found to be equal to the product of the magnitude of the other force, as well as the effort arm.
In technical terms, the product of a force is referred to as the moment of force with respect to its effort. The theory of moments states that equilibrium is established whenever the sum of the moments of the forces acting in an anti-clockwise direction equals the sum of the moments of the forces acting in a clockwise direction.
As a result, in order to overcome a very large force at a large distance, a very small force at a large distance from the fulcrum.
Types of Levers
According to where the load and effort are located with respect to the fulcrum, there are three types or classes of lever:
- First-Class Lever
- Second Class Lever
- Third Class Lever
First Class Lever
Also known as Class 1 or 1st class lever, the load is at one end of the beam, and the effort is at the other end. The fulcrum is between the load and effort.
Depending upon the position of the fulcrum, the effort can be high or low. If the fulcrum is closer to the load than the effort, the effort is low. The effort is high if the fulcrum is closer to the effort than the load.
Example:
Here are some of the examples of first-class levers which are as follows:
- Pliers
- Scissors
- Crowbar
- Claw hammer
- See-saw
- Weighing balance
- The hand pushing objects or seesaws, crowbars.
- Using scissors shows the use of first-class levers.
- A wheel and an axle.
- Pulling a nail out of a wooden plank.
Second Class Lever
Also known as a Class 2 or 2nd class lever, the fulcrum is at one end of the beam, and the effort is at the other end. The load is located between the fulcrum and the effort.
The position of the load affects the effort. If the load is closer to the fulcrum than the effort, the effort is low. The effort is high if the load is closer to the effort than the fulcrum.
Example:
- Wheelbarrow
- Staplers
- Doors or gates
- Bottle openers
- Nutcracker
- Nail clippers
Third Class Lever
Also known as Class 3 or 3rd class lever, the fulcrum is at one end of the beam, and the load is at the other end. The effort is located between the fulcrum and load.
The effort depends upon its position. The effort is high if it is closer to the load than the fulcrum. The effort is high if it is closer to the fulcrum than the load.
Example:
- Fishing rod
- A broom
- A baseball bat
- A bow and arrow
- Human jaw
What Are the Uses of a Lever?
The simplest devices, like levers, are employed to complete tasks quickly. Leverage is the ability to increase an input force to produce a stronger output force.
We know that there are different kinds of levers depending on the force, weight, and fulcrum point. Each tool that is used to complete a task falls into one of these categories.
Objects are typically moved or lifted using a lever. In some cases, pushing against items without really moving them is used. By applying a little force over a wider distance at the other end, levers can be used to apply a huge force over a short distance at one end.
The following are some common uses of levers:
- Levers make it simple to cut, remove, and lift objects that are tight.
- Common levers for removing nails from wood or other tough surfaces include hammer claws.
- Wheelbarrows are useful on a daily basis as they facilitate the movement of heavy or hefty items.
- Even though the objects are not particularly heavy, levers like tweezers make it simple to lift or remove them.
- Levers that apply force to cut or separate material include scissors.
Teeter-totters, wheelbarrows, scissors, pliers, bottle openers, mops, brooms, shovels, nutcrackers, and sporting goods like baseball bats, golf clubs, and hockey sticks are all examples of levers in daily life. You can even use your arm as a lever.