The lever is one of the most basic and widely used simple machines. It consists of a rigid bar that can rotate around a support point called the fulcrum or fulcrum. The lever is used to amplify or change the direction of a force applied to an object.
Levers are found in many everyday tools and machines, from pliers to scissors to a saw. They are also used in more complex applications such as cranes and heavy-duty machines.
A lever consists of three main components: the fulcrum, the force application point (where the force is applied), and the resistance application point (where the load or object to be lifted is located). These components can vary in their relative position and will determine the type of lever.
Types of levers
There are three types of levers, depending on the relative position of the components:
First class or force lever
In this type, the fulcrum is between the applied force and the resistance. By applying a force at one end, a force is generated at the opposite end to lift the resistance.
A common example is an arm scale.
Second class or resistance lever
The resistance lies between the fulcrum and the applied force. By applying a force at one end, resistance is raised at the opposite end.
An example of a second-class lever is a forklift, where the fulcrum is on one of the rear wheels, the load is on the platform, and the force is applied to the handles.
Third class lever
The applied force lies between the fulcrum and the resistor. This type allows an amplification of the force, but at the cost of decreasing the speed and range of the movement.
An example of a third-class lever is the human forearm, where the arm muscles act as the applied force, the elbow is the fulcrum, and the load is in the hand.
What is a lever used for?
A lever is used to facilitate or amplify the application of a force to move or lift objects. These simple machines allow you to change the direction, intensity, and speed of an applied force.
The applications of the levers are diverse and are found in many areas of daily life, engineering, industry and other fields. Some common uses include:
Lifting Heavy Objects: These are used to lift heavy objects more efficiently. Applying a force at one end amplifies the force at the opposite end, making it possible to lift objects that would otherwise be difficult or impossible to move.
Hand Tools: Many hand tools, such as pliers, pliers, tweezers, and screwdrivers, use levers to make it easier to apply force and do more precise work. In this way, the tools allow for better grip and control, and reduce the amount of force required to perform a given task.
Industrial machines: In industry, levers are used in various machines to perform heavy work. For example, cranes, forklifts, and hoists use this type of simple machine to lift and move heavy loads more efficiently and safely.
Balance and Stability: Levers as simple machines are also used to maintain balance and stability in various applications. For example, in a children's playground seesaw.
Biomechanics of the human body: Bones and joints act as levers in the musculoskeletal system, allowing movement of muscles and performance of physical activities.
Examples of levers
Here are some examples that we can find on a day-to-day basis:
Tweezers: Tweezers, such as eyebrow tweezers or hair clips, are examples of first-class levers. The fulcrum is at the fulcrum between the ends of the clamp, the force is applied at one end, and the resistance (such as a hair or an eyebrow) is at the other end.
Scissors: Scissors are another example of a first class lever. The fulcrum is located on the screw or pivot that connects the two blades. The force is applied in the handles and the resistance is in the cutting blades.
Arm scale: The arm scale used to measure weight is a classic example of the first kind. The fulcrum is at the center of the scale, the force is applied at one end, and the resistance (the object to be weighed) is at the other end.
Forklift: A forklift uses a lever of the second kind. The fulcrum is at the rear wheel, the resistance is found in the load being lifted on the platform, and the force is applied to the handles of the dolly.
Can Opener: A manual can opener is an example of the second genre. The fulcrum is at the point where the can opener clamps onto the rim of a can, the resistance is at the can lid, and the force is applied at the can opener handle.
Human Forearm: The human forearm acts as a third-class lever. The fulcrum is in the elbow, the force is applied through the muscles, and the resistance is in the hand or fingers when you grasp an object.