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Mechanical Energy

Mechanical energy

In  physics, mechanical energy  is the sum  of  potential energy  and  kinetic energy . This energy is associated with the movement and position of an object. The principle of mechanical energy says that in an isolated system where there is only  one conservative force,  then the magnitude of the mechanical energy is constant.

If an object moves in the opposite direction to the conservative force, then the potential energy increases. It would be the case of a rocket, the conservative force, in this case, would be the force of gravity. If the  speed of the object changes, then its kinetic energy also changes.  

However, in all real systems,   non-conservative styles   like  friction forces  will appear, but their value is often ignored. This means that the value of mechanical energy can be considered constant. In  elastic collisions , mechanical energy will be stored, but in  non- elastic collisions  , part of the mechanical energy is converted into thermal energy, in the form of heat. The relationship between the loss of mechanical energy ( dissipation ) and the increase in  temperatures was  discovered by  James Prescott Joule .

Many of the tools are used to convert mechanical energy from and to other forms of energy, such as electric motors  that convert  electrical  energy into mechanical energy, the  electric motor  converts mechanical energy into  electrical energy,  and  heat engines or Steam engines  ( steam engine) transform  heat  into mechanical energy.

Differences of Mechanical Energy with Other Types of Energy 

The grouping of energy into various types often follows the boundaries of the evaluation branch of the natural sciences. In this sense we could establish the following relationship of types of energy.

  • Chemical energy is a type of potential energy stored in  chemical bonds .
  • Energy  nuclear , nuclear energy is the energy stored in particle interactions within  of the atomic nucleus. Its use is obtained through nuclear fission and nuclear fusion reactions.
  • Electromagnetic energy,  this type of energy comes in the form  of electric charges,  magnetic fields  and  photons. Its development is studied in the field of electromagnetism .
  • Various forms of energy in  quantum mechanics ; for example,  the energy level of an electron  within an atom.

Mechanical Energy as Work Capacity.

An object that has mechanical energy is capable of doing work . In fact, mechanical energy is often defined as the ability to work. Any object that possesses mechanical energy, whether in the form of potential energy or kinetic energy, is capable of functioning. That is, its mechanical energy allows that object to apply a force to another object to make it move.

Numerous examples can be given of how an object with mechanical energy can exploit that energy to apply a force to make another object move.

A classic example is the heavy sphere of a demolition machine.

The breaking ball is a massive object that swings from a high position that allows it to swing toward the building structure or other objects to demolish it.

In the event of a collision with the structure, the sphere exerts a force on it that causes the wall of the structure to break.

Although a hammer is a tool that uses mechanical energy to get work done.

The mechanical energy of a hammer gives the hammer its ability to apply force to a nail to make it move. Since the hammer has mechanical energy (in the form of kinetic energy), it is capable of doing work on the nail. Mechanical energy is the ability to work.

Another example illustrating how mechanical energy is the ability of an object to work can be seen one night at a bowling alley.

The mechanical energy of a bowling ball gives the ball the ability to apply force to a pin to make it move. Since the massive sphere has mechanical energy (in the form of kinetic energy), it can work on the pin. Mechanical energy is the ability to work.

A toy gun that shoots arrows is another example of how mechanical energy from one object can work on another object. When a gun is loaded and the springs are compressed, it has mechanical energy.

The mechanical energy of the compressed springs gives the springs the ability to apply a force to the dart to make it move. Because springs have mechanical energy (in the form of elastic potential energy), it can do the job of the arrow. Mechanical energy is the ability to work.

A common scene in some parts of the countryside is a "wind farm." High-speed winds are used to work on the turbine blades of a so-called wind farm.

The mechanical energy of moving air gives the air particles the ability to apply a force and cause the blades to move.

As the blades rotate, their energy is subsequently converted into electrical energy (a non-mechanical form of energy) and supplied to homes and industries to run appliances.

Since the moving wind has mechanical energy (in the form of kinetic energy), it can work on the blades. Again, mechanical energy is the ability to work.

Total Mechanical Energy

As already mentioned, the mechanical energy of an object can be the result of its motion (kinetic energy = KE) and / or the result of its stored position energy (potential energy = PE).

The total amount of mechanical energy is simply the sum of the potential energy and the kinetic energy. This sum is simply called total mechanical energy (TME for short).

TME = PE + KE

As discussed earlier, there are two forms of potential energy discussed in our course: gravitational potential energy and elastic potential energy. For this reason, the above equation can be rewritten:

TME = PEgrav + PEspring + KE

There are conditions where the total mechanical energy will be a constant value and conditions where it will be a variable value.

For now, remember that total mechanical energy is the energy an object possesses due to its motion or its stored positional energy.

The total amount of mechanical energy is simply the sum of these two forms of energy.

Finally, to summarize what has already been said several times, an object with mechanical energy is capable of working on another object.

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Published: November 14, 2017
Last review: October 26, 2020