We explain what mechanical energy is and how it can be classified. Also, examples and mechanical potential and kinetic energy.
What is mechanical energy?
mechanical energy It is the sum of the kinetic energy and the potential energy of a body or system. Kinetic energy is the energy that moving bodies have, since it depends on their speeds and masses. Potential energy, on the other hand, is associated with the work of forces that are called conservative, such as elastic and gravitational forces, which depend on the mass of the bodies and their position and structure.
The Principle of Conservation of Energy establishes that mechanical energy is conserved (remains constant) as long as the forces acting on the body or system are conservative, that is, they do not cause the system to lose energy. This principle can be written mathematically as follows:
Emec = Ec + Ep = cte
where Ec is the kinetic energy of the system and Ep its potential energy, which can be gravitational, elastic, electrical, etc.
This relationship does not hold if the system is affected by non-conservative forces. For example, in the case of movements on friction surfaces (like most surfaces), kinetic energy is dissipated as heat. The mechanical energy of a system can also be lost in the form of heat, for example in thermodynamic systems in which mechanical energy can be converted into thermal energy.
mechanical energy It is frequently used to carry out work or convert it into other forms of energy, as is the case of hydraulic energy (when man takes advantage of the potential energy of falling water to do work). Another example is wind energy or tidal energy, which uses the kinetic energy of the wind and tides to transform them into another type of useful energy.
See also: Elasticity
Types of mechanical energy
Mechanical energy is the sum of the following energies:
- Kinetic energy It is the energy possessed by objects or a system in motion, and which depends on its speed and mass. For example: a ball in motion.
- Potential energy It is the energy associated with the position of a body within a conservative field of forces, such as gravitational, elastic, electrical, etc. In turn, potential energy can be two types:
- gravitational potential energy. It is the energy that is due to the action of gravity on bodies. For example: an object that falls from a certain height.
- elastic potential energy. It is the energy possessed by systems deformed by a force. The energy remains in the system until the force is no longer applied and thus the system returns to its original shape, transforming the elastic energy into kinetic energy. For example: a spring that stretches or contracts by means of an external force that, when it is no longer applied, allows the spring to return to its normal, equilibrium position.
Examples of mechanical energy
Some possible examples of mechanical energy in its different forms are the following:
- A roller coaster car At its highest point, the cart will have accumulated enough gravitational potential energy (due to height) to fall freely a second later and convert it all into kinetic energy (due to movement) and reach breakneck speeds.
- A windmill The kinetic energy of the wind provides thrust to the mill blades that is converted into mechanical work: turning the gear that will grind the grains further down.
- A pendulum The gravitational potential energy of the weight is converted into kinetic energy to make it move along its path, conserving the total mechanical energy.
- a springboard. The bather who dives off a trampoline uses his weight (gravitational potential energy) to deform the trampoline downwards (elastic potential energy) and it, upon recovering its shape, pushes him upwards, increasing his height (more gravitational potential) which act It is then converted into kinetic energy during free fall into the water.
Mechanical kinetic and potential energy
As has already been said, the mechanical energy It involves two energies: kinetic and potential.
The first is calculable using the simple formula of Ec = ½ m. v2 and its unit of measurement in the International System will be Joules (J).
On the other hand, potential energy is the amount of energy stored in the system due to its particular configuration or its positioning with respect to a field of forces (gravitational, elastic or electromagnetic). This energy can be converted into other forms of energy, such as kinetic energy itself.
