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The joule (/ dʒ uː l / JOOL, or / dʒ aʊ l / JOWL; symbol: J) is the unit of energy in the International System of Units (SI). [1] It is equal to the amount of work done when a force of one newton displaces a mass through a distance of one metre in the direction of that force.
The ancient Greek understanding of physics was limited to the statics of simple machines (the balance of forces), and did not include dynamics or the concept of work. During the Renaissance the dynamics of the Mechanical Powers, as the simple machines were called, began to be studied from the standpoint of how far they could lift a load, in addition to the force they could apply, leading ...
Energy is defined via work, so the SI unit of energy is the same as the unit of work – the joule (J), named in honour of James Prescott Joule [1] and his experiments on the mechanical equivalent of heat. In slightly more fundamental terms, 1 joule is equal to 1 newton metre and, in terms of SI base units
PV work is often measured in units of litre-atmospheres where 1 L·atm = 101.325 J. However, the litre-atmosphere is not a recognized unit in the SI system of units, which measures P in pascals (Pa), V in m 3, and PV in joules (J), where 1 J = 1 Pa·m 3. PV work is an important topic in chemical thermodynamics.
The first law of thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes.The law distinguishes two principal forms of energy transfer, heat and thermodynamic work, that modify a thermodynamic system containing a constant amount of matter.
Power is the rate with respect to time at which work is done; it is the time derivative of work: =, where P is power, W is work, and t is time. We will now show that the mechanical power generated by a force F on a body moving at the velocity v can be expressed as the product: P = d W d t = F ⋅ v {\displaystyle P={\frac {dW}{dt}}=\mathbf {F ...
In particular Joule had experimented on the amount of mechanical work generated by friction needed to raise the temperature of a pound of water by one degree Fahrenheit and found a consistent value of 778.24 foot pound force (4.1550 J·cal −1). Joule contended that motion and heat were mutually interchangeable and that, in every case, a given ...
The erg is a unit of energy equal to 10 −7 joules (100 nJ). It is not an SI unit, instead originating from the centimetre–gram–second system of units (CGS). Its name is derived from ergon (ἔργον), a Greek word meaning 'work' or 'task'. [1] An erg is the amount of work done by a force of one dyne exerted for a distance of one centimetre.