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The foot (standard symbol: ft) [1] [2] is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, ′, is commonly used to represent the foot. [3] In both customary and imperial units, one foot comprises 12 inches, and one yard comprises three feet.
A board foot is a United States and Canadian unit of approximate volume, used for lumber. It is equivalent to 1 inch × 1 foot × 1 foot (144 cu in or 2,360 cm 3). It is also found in the unit of density pounds per board foot. In Australia and New Zealand the terms super foot or superficial foot were formerly used for this unit. The exact ...
There are anecdotal objections to the use of metric units in carpentry and the building trades, on the basis that it is easier to remember an integer number of inches plus a fraction, rather than a measurement in millimeters, [9] or that foot-inch measurements are more suitable when distances are frequently divided into halves, thirds, and ...
This is convenient because one pound mass exerts one pound force due to gravity. Note, however, unlike the other systems the force unit is not equal to the mass unit multiplied by the acceleration unit [11] —the use of Newton's second law, F = m ⋅ a, requires another factor, g c, usually taken to be 32.174049 (lb⋅ft)/(lbf⋅s 2).
In the BG system, force, rather than mass has a base unit while the slug is a derived unit of inertia (rather than mass). [54] On the other hand, the EE system uses a different approach and introduces the acceleration due to gravity (g) into its equations. Both these approaches led to slight variations in the meaning of the pound-force (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).
The avoirdupois units of mass and weight differ for units larger than a pound (lb). The British imperial system uses a stone of 14 lb, a long hundredweight of 112 lb and a long ton of 2,240 lb. The stone is not a measurement of weight used in the US. The US customary system uses the short hundredweight of 100 lb and short ton of 2,000 lb.
The metric ton is the name used for the tonne (1000 kg, 2 204.622 62 lb), which is about 1.6% less than the long ton. The US customary system also includes the kip, equivalent to 1,000 pounds of force, which is also occasionally used as a unit of weight of 1,000 pounds (usually in engineering contexts).