Mechanical energy

Mechanical energy is a form of energy typically described as a combination of kinetic energy and potential energy. In other words, mechanical energy is the sum of an object’s kinetic and potential energy. This means that an object has mechanical energy whether it is moving or staying in position relative to a zero potential energy position. Mechanical energy can also be thought of as the ability of an object to do work. In this sense, work is done when a force acts on an object and causes it to move, change shape, or do something else physical. Taken from this perspective, mechanical energy is the sum of kinetic and potential energy in an object used to do work. Further, the principle of conservation of mechanical energy states that the total mechanical energy of an object or system remains unchanged as long as the net work done by a non-conservative force like friction or air resistance is zero.

Background

Understanding mechanical energy requires some background on energy itself. There are two different types of energy. These types are known as potential energy and kinetic energy. Potential energy is energy that is stored within an object as a result of its position. It is referred to as potential energy because it has the potential to be converted into other forms of energy. There are three types of potential energy. These include gravitational, electric, and elastic potential energy. Gravitational potential energy is energy that is stored in an object due to its vertical position. Electric potential energy arises from the electrical charges of atoms and how they interact with one another. Elastic potential energy is energy that is stored in elastic materials as a result of stretching and compression. A ball sitting at the top of a slope is one example of common gravitational potential energy. Potential energy is stored in the ball because of its position at the top of the slope and its potential to turn into kinetic energy if it were to roll down the slope. A compressed spring is another example of potential energy. Such a spring possesses potential energy because it has been compressed. If the spring were released, it would rapidly decompress as its potential energy is converted into kinetic energy.

While potential energy is energy that is stored within an object when it is at rest, kinetic energy is energy that is possessed by an object when it is in motion. Any object that is in horizontal or vertical motion has kinetic energy. In fact, the term kinetic is itself derived from kinesis, the Greek word for motion. There are many forms of kinetic energy. Some of these include vibrational, rotational, and translational kinetic energy. Vibrational kinetic energy refers to motion that arises due to some sort of vibration. Rotational kinetic energy arises as a result of rotational motion. Translational kinetic energy is energy that is created by motion from one location to another. In the above example of a ball sitting at the top of a slope, the ball’s potential gravitational potential energy is transformed into translational kinetic energy as it rolls down the slope.

Overview

Mechanical energy is the energy an object possesses due to its position or motion. It is the sum of an object’s kinetic and potential energy. As such, mechanical energy can itself be either potential or kinetic in nature. Objects can even possess both potential and kinetic mechanical energy at the same time. The mechanical energy of a moving car, for example, is kinetic in nature because of its motion. On the other hand, a book sitting on a shelf possesses mechanical energy that is potential in nature because of its position above the ground. A football that is flying through the air possesses mechanical energy that is both kinetic and potential in nature because of its high-speed, forward motion and its vertical position above the ground.

Mechanical energy can also be described as the ability to do work. Any object that possesses mechanical energy is capable of doing some sort of work. Specifically, mechanical energy enables an object to apply a force to and thereby displace another object. A hammer and nail being driven into a floorboard serve as a simple example of this phenomenon. The hammer possesses mechanical energy both because of its vertical position above the ground and its motion when it is swung. Ultimately, the hammer’s mechanical energy is used to strike the nail and displace it by forcing it deeper into the floorboard. Bowling balls offer a similar example of the relationship between mechanical energy and work. The mechanical energy of a rolling bowling ball gives it the ability to do the work of striking and knocking down the pins at the end of the lane.

When studying mechanical energy, it is important to understand the principle of conservation of mechanical energy. This principle states that the mechanical energy of an isolated physical or thermodynamic system remains constant in the absence of any non-conservative force. Non-conservative refers to any force like friction or air resistance that removes energy from an isolated system. According to the principle of conservation of mechanical energy, mechanical energy can neither be created nor destroyed in an isolated system.

While it cannot be created or destroyed, it can be converted into other types of energy with the help of various modern technologies. Steam engines, for example, can convert mechanical energy into heat energy. Hydroelectric plants use the mechanical energy of water to generate electrical energy. Internal combustion engines convert chemical energy into mechanical energy through the burning of fuel. Windmills harness the wind’s mechanical energy to generate electrical energy.

It is also possible to convert other forms of energy into mechanical energy. Turbines can be used to convert the kinetic energy of steam into mechanical energy. Electric motors can be used to convert electrical energy into mechanical energy.

Mechanical energy is typically measured in units known as joules. The joule was named in honor of James Joule, an English physicist and mathematician who was responsible for discovering the link between the increase of heat energy and the loss of mechanical energy. It was Joule’s work that eventually led to the development of the law of conservation of energy.

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