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Energy (from Ancient Greek ἐνέργεια (enérgeia) 'activity') is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat and light.
A physical body as a whole is assumed to have such quantitative properties as mass, momentum, electric charge, other conserved quantities, and possibly other quantities. An object with known composition and described in an adequate physical theory is an example of physical system.
For example, when a machine (not a part of the system) lifts a system upwards, some energy is transferred from the machine to the system. The system's energy increases as work is done on the system and in this particular case, the energy increase of the system is manifested as an increase in the system's gravitational potential energy. Work ...
Energy – in physics, this is an indirectly observed quantity often understood as the ability of a physical system to do work on other physical systems. [ 1 ] [ 2 ] Since work is defined as a force acting through a distance (a length of space), energy is always equivalent to the ability to exert force (a pull or a push) against an object that ...
energy: joule (J) Young's modulus: pascal (Pa) or newton per square meter (N/m 2) eccentricity: unitless Euler's number (2.71828, base of the natural logarithm) unitless electron: unitless elementary charge: coulomb (C) force: newton (N) Faraday constant: coulombs per mole (C⋅mol −1)
Rate of transfer of energy per unit time watt (W) L 2 MT −3: extensive, scalar Pressure: p: Force per unit area pascal (Pa = N/m 2) L −1 MT −2: intensive, scalar (Radioactivity) Activity: A: Number of particles decaying per unit time becquerel (Bq = Hz) T −1: extensive, scalar (Radiation) Dose: D: Ionizing radiation energy absorbed per ...
Internal energy: The energy contained within a body of matter or radiation, excluding the potential energy of the whole system, and excluding the kinetic energy of the system moving as a whole. Heat : Energy in transfer between a system and its surroundings by mechanisms other than thermodynamic work and transfer of matter.
In physical sciences, mechanical energy is the sum of potential energy and kinetic energy. The principle of conservation of mechanical energy states that if an isolated system is subject only to conservative forces , then the mechanical energy is constant.