Simple Machines and Mechanical Principles Explained

1. Machines and Mechanisms

A machine is a device capable of reducing the effort required to conduct a task. Mechanisms are groups of mechanical elements, each of which performs a specific function or task within the machine. Machines can be classified as follows:

• Simple machines: Devices that only have one support point.
• Complex machines: Systems formed by two or more fundamental simple machines.

Law of Simple Machines

In a simple machine, the work done by the driving forces equals the work done by the resisting forces.

2. Lever

The lever is a simple machine consisting of a rigid rod that can rotate around a support point or fulcrum. The following components can be distinguished in a lever:

• Power
• Resistance
• Power arm
• Resistance arm

Law of the Lever

The product of the power and the power arm is equal to the product of the resistance and the resistance arm.

Types of Levers

• First-class lever: The fulcrum is located between the power and the resistance.
• Second-class lever: The resistance is located between the fulcrum and the power.
• Third-class lever: The power is located between the resistance and the fulcrum.
• Multiple levers: Systems formed by the combination of several levers of the same or different classes.

3. Inclined Plane and Wedge

The inclined plane is a simple machine consisting of a flat surface forming an angle with the horizontal. The product of the power by the length of the incline is equal to the product of the resistance by the height of the plane.

4. Screw

The screw is a simple machine consisting of an inclined plane wrapped in a uniform and constant manner around a cylindrical surface. The propeller of the screw is called the thread. The outgoing spiral is the thread crest, the bottom is the root, and the inner side surfaces are called sides.

Types of Threads

• Profile: The section of the thread profile is usually triangular, but square and trapezoidal profiles also exist depending on the application.
• Direction of rotation: The direction required to advance the screw can be clockwise or counter-clockwise.
• Number of threads: A screw can have one or more threads in parallel coiled around the core, which allows for faster progression.
• Pitch: The thread pitch is the distance between two consecutive threads.