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Systems of measure either define mass and derive a force unit or define a base force and derive a mass unit [1] (cf. poundal, a derived unit of force in a mass-based system). A slug is defined as a mass that is accelerated by 1 ft/s 2 when a net force of one pound (lbf) is exerted on it.
The avoirdupois weight system is thought to have come into use in England around 1300. [citation needed] It was originally used for weighing wool. In the early 14th century several other specialized weight systems were used, including the weight system of the Hanseatic League with a 16-ounce pound of 7200 grains and an 8-ounce mark.
In the metric system, there are only a small number of basic measures of relevance to cooking: the gram (g) for weight, the liter (L) for volume, the meter (m) for length, and degrees Celsius (°C) for temperature; multiples and sub-multiples are indicated by prefixes, two commonly used metric cooking prefixes are milli-(m-) and kilo-(k-). [17]
The pound or pound-mass is a unit of mass used in both the British imperial and United States customary systems of measurement.Various definitions have been used; the most common today is the international avoirdupois pound, which is legally defined as exactly 0.453 592 37 kilograms, and which is divided into 16 avoirdupois ounces. [1]
The avoirdupois system served as the general system of mass and weight. In addition to this, there are the troy and the apothecaries' systems. Troy weight was customarily used for precious metals, black powder, and gemstones. The troy ounce is the only unit of the system in current use; it is used for precious metals.
Troy weight, avoirdupois weight, and apothecaries' weight are all built from the same basic unit, the grain, which is the same in all three systems. However, while each system has some overlap in the names of their units of measure (all have ounces and pounds), the relationship between the grain and these other units within each system varies.
The definition of units of weight above a pound differed between the customary and the imperial system - the imperial system employed the stone of 14 pounds, the hundredweight of 8 stone [Note 6] and the ton of 2240 pounds (20 hundredweight), while the customary system of units did not employ the stone but has a hundredweight of 100 pounds and ...
Units for other physical quantities are derived from this set as needed. In English Engineering Units, the pound-mass and the pound-force are distinct base units, and Newton's Second Law of Motion takes the form = where is the acceleration in ft/s 2 and g c = 32.174 lb·ft/(lbf·s 2).