Sum of a system's kinetic energy (KE) and potential energy (PE). Mechanical energy is constant in a system that experiences no dissipative forces such as friction or air resistance. For example, a swinging pendulum that experiences only gravitation has greatest KE and least PE at the lowest point on the path of its swing, where its speed is greatest and its height least. It has least KE and greatest PE at the extremities of its swing, where its speed is zero and its height is greatest. As it moves, energy is continuously passing back and forth between the two forms. Neglecting friction and air resistance, the pendulum's mechanical energy is constant.
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When a given amount of mechanical energy is transferred (such as when throwing a ball, lifting a box, crushing a soda can, or stirring a beverage) it is said that this amount of mechanical work has been done. Both mechanical energy and mechanical work are measured in the same units as energy in general. It is usually said that a component of a system has a certain amount of "mechanical energy" (i.e. it is a state function), whereas "mechanical work" describes the amount of mechanical energy a component has gained or lost.
The conservation of mechanical energy is a principle which states that under certain conditions, the total mechanical energy of a system is constant. This rule does not hold when mechanical energy is converted to other forms, such as chemical, nuclear, or electromagnetic. However, the principle of general conservation of energy is so far an unbroken rule of physics - as far as we know, energy cannot be created or destroyed, only changed in form.
To calculate the energy of a system without any simplifying assumptions would require examining the state of all elementary particle(s) and considering all four fundamental interactions). This is usually only done for very small systems, such as those studied in particle physics.
In certain cases, it can be unclear what counts as "mechanical" energy. For example, is the energy stored in the structure of a crystal "mechanical" or "chemical"? Scientists generally use these "types" as convenient labels which clearly distinguish between different phenomena. It is not scientifically important to decide what is "mechanical" energy and what is "chemical". In these cases, usually there is a more specific name for the phenomenon in question. For example, in considering two bonded atoms, there are energy components from vibrational motion, from angular motions, from the electrical charge on the nuclei, secondary electromagnetic considerations like the Van der Waals force, and quantum mechanical contributions concerning the energy state of the electron shells.
Stommel's Box Model of Thermohaline Circulation Revisited-The Role of Mechanical Energy Supporting Mixing and the Wind-Driven Gyration
Apr 01, 2008; ABSTRACT The classical two-box model of Stommel is extended in two directions: replacing the buoyancy constraint with an energy...
WIPO ASSIGNS PATENT TO SIEMENS FOR "TIRE WITH DEVICE FOR PROVIDING MECHANICAL ENERGY, METHOD FOR PROVIDING MECHANICAL ENERGY BY USING THE TIRE, AND THE USE OF THE MECHANICAL ENERGY" (GERMAN INVENTORS)
Feb 08, 2011; GENEVA, Feb. 8 -- Publication No. WO/2011/012429 was published on Feb. 03. Title of the invention: "TIRE WITH DEVICE FOR...