Simple Machines and Mechanical Energy Principles

Simple Machines: Fundamentals of Mechanics

Simple machines are fundamental mechanisms. They are characterized by the exchange of mechanical work (involving some of their moving elements), and all their solid parts are rigid.

Levers: Principles and Classes

A lever is a simple machine formed by a rigid bar that can turn around a support point, known as the fulcrum. In all levers, there is a point where the body to be moved is placed, which we call resistance, and another point where force is applied to move the load, which we call power or effort. The distances from the fulcrum to the application points of the load and power are called arms.

Types of Levers Explained

1. First Class Levers: The fulcrum is located between the load and the applied force (e.g., seesaw, scissors, balance, pliers).
2. Second Class Levers: The load is located between the fulcrum and the applied force (e.g., fishing rod, stapler).
3. Third Class Levers: The applied force is located between the fulcrum and the load or resistance point (e.g., fishing rod, tweezers, pedal).

Pulleys: Force and Motion

A pulley is a disc with a grooved rim through which a rope or chain passes. It revolves around a central fixed axis and is supported by a frame called a block. The main advantage of a pulley is that it allows us to exert force in a much more comfortable way. A single pulley is a good example of this type of mechanism. For instance, when we draw a bucket full of water from a well, we must pull with a force equal to the weight of the bucket.

Double Hoists: Lifting Systems

A double hoist system is formed by two pulleys and two ropes.

Wheel and Axle: Rotational Mechanics

The wheel and axle is another simple machine whose operation can be explained by moments. A wheel and axle is formed by a horizontal cylinder of radius (r) that rotates on an axis.

Wedge: Splitting and Fastening

A wedge is a double inclined plane, where the force perpendicular to the base is multiplied and transmitted to the faces of the wedge.

Inclined Plane: Reducing Effort

An inclined plane is a ramp that allows raising objects with less effort.

Hoist Systems: Lifting Heavy Loads

A hoist is a combination of pulleys designed to lift a large weight with minimal force. It typically consists of a group of pulleys, including one fixed and one mobile pulley, forming a potential hoist system. In such systems, a single rope often passes through both fixed and mobile pulleys. In an exponential hoist, the rope passes through each mobile pulley sequentially.

Screw: Fastening and Mechanical Advantage

A screw is a mechanical fastening device formed by a threaded incline around a cylinder or cone.

Screw Components and Function

• Thread: The ridges formed by the inclined plane.
• Pitch: The distance between two crests.

Mechanical Energy Accumulators

Mechanical energy accumulators are devices that can store or accumulate a certain amount of mechanical energy locally and return it when needed.

Flywheel: Storing Rotational Energy

A flywheel consists of a wheel or a disc, often made of cast iron or steel, mounted on the motor's crankshaft, which rotates with it.

Flywheel Operating Principle

Whenever the work supplied by the engine is greater than the resistance during a time interval, the speed of the machine increases. Conversely, when the work is less than the resistance, the speed decreases.

Flywheel as an Engine Booster

Certain engines, such as steam engines and internal combustion engines, supply work intermittently. However, the work to be done by the machines they power is practically constant (e.g., engine combustion). A four-stroke engine produces power in four phases:

1. Intake
2. Compression
3. Combustion (Explosion)
4. Exhaust

However, the crankshaft receives energy to turn in only one of these phases: the combustion phase.

Elastic Elements: Springs and Their Role

Elastic elements, such as springs, play an important role in machines and are used for a huge variety of jobs.

Definition of Elastic Elements

Elastic elements are components that are deformed by the action of a force and regain their original shape when the deforming force ceases.