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An overview of ranges of mass. To help compare different orders of magnitude, the following lists describe various mass levels between 10 −67 kg and 10 52 kg. The least massive thing listed here is a graviton, and the most massive thing is the observable universe.
The specific weight, also known as the unit weight (symbol γ, the Greek letter gamma), is a volume-specific quantity defined as the weight W divided by the volume V of a material: = / Equivalently, it may also be formulated as the product of density, ρ, and gravity acceleration, g: = Its unit of measurement in the International System of Units (SI) is newton per cubic metre (N/m 3), with ...
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 slug is a derived unit of mass in a weight-based system of measures, most notably within the British Imperial measurement system and the United States customary measures system. 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 ...
For example, in a recipe that calls for 10 pounds of flour and 5 pounds of water, the corresponding baker's percentages are 100% for the flour and 50% for the water. Because these percentages are stated with respect to the weight of flour rather than with respect to the weight of all ingredients, the sum of these percentages always exceeds 100%.
The conversion between different SI units for one and the same physical quantity is always through a power of ten. This is why the SI (and metric systems more generally) are called decimal systems of measurement units. [10] The grouping formed by a prefix symbol attached to a unit symbol (e.g. ' km ', ' cm ') constitutes a new inseparable unit ...
Molecular weight (M.W.) (for molecular compounds) and formula weight (F.W.) (for non-molecular compounds), are older terms for what is now more correctly called the relative molar mass (M r). [8] This is a dimensionless quantity (i.e., a pure number, without units) equal to the molar mass divided by the molar mass constant .
When the molecular weight is given with the unit Da, it is frequently as a weighted average similar to the molar mass but with different units. In molecular biology, the mass of macromolecules is referred to as their molecular weight and is expressed in kDa, although the numerical value is often approximate and representative of an average.