The kilogram, originally defined as the mass of one cubic decimeter of water at the temperature of maximum density, was known as the Kilogram of the Archives.
The primary standard of mass for this country is United States Prototype Kilogram 20, which is a platinum-iridium cylinder kept at NIST. The kilogram (kg) is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015 ×10 −34 when expressed in the unit J s, which is equal to kg m 2 s −1, where the meter and the second are defined in terms of c and ∆ν Cs. National Type Evaluation Program (NTEP).National Conference on Weights and Measures (NCWM).External Resources for Weights and Measures Expand or Collapse.Fuels and Lubricants Subcommittee (FALS).National Legal Metrology Expand or Collapse.Laboratory Metrology Expand or Collapse.International Legal Metrology Expand or Collapse.OWM Products and Services Expand or Collapse.Use your knowledge and skills to help others succeed.ĭon't be wasteful protect our environment. Displacement Equations for Falling Objects.Displacement-Velocity Gravity Equations.Gravity topics Mini-Quiz: Confusion about Units of Mass and Weight Please include it as a link on your website or as a reference in your report, document, or thesis. Top-rated books on Advanced Gravity Physics Top-rated books on Simple Gravity Science (Notice: The School for Champions may earn commissions from book purchases) United States customary units - Wikipedia The Difference Between Weight and Mass. Pounds as weight is commonly used, but it really refers to pound-force.Īs a student of science, you need to be careful in what you call things. In the American system, the unit of mass is the pound-mass. Weight is stated as newtons, kilograms-force, or kilograms-weight, not simply kilograms.
In the metric system, the unit of mass is the kilogram. It is important to state units of mass and weight in a manner that will not cause confusion in calculations. The international avoirdupois pound is defined as about 0.45 kilogram-mass.One kilogram-force is approximately 2.2 pound-force.When you convert between the British/American system and the metric system, you need to be careful which definitions of weight and mass are used for the conversion. Thus, if an object weighs 64 lbs, its mass is 2 pounds-mass:Ħ4 lb-f = (2 lb)* (32 ft/s 2) Conversion between systems g is the acceleration due to gravity on the Earth, g = 32 ft/s 2.The relationship between the weight of an object and its mass in the English/American system is: Calling the mass of the object a pound-mass could alleviate that confusion. This can result in confusion when making calculations. Also, some Physics textbooks say that a pound is a unit of weight or force, as in foot-pounds for torque. However, in common use, people often state weight in terms of pounds. The avoirdupois pound ( lb) is legally defined as a measure of mass in the British Imperial measurement system, as well as the United States system of units. Thus, if an object has a mass of 50 kg, its weight is 490 N or 490 kg-force:Ĥ90 kg-f = (50 kg )*(9.8 meters/s 2) Confusion concerning pounds g is the acceleration due to gravity on the Earth, g = 9.8 m/s 2.
W is weight in newtons ( N) or kilograms-force ( kg-f).The relationship between the weight of an object and its mass in the metric system is: Note that designating kilogram-mass as kg-m could result in confusion with kg-meters. When they say "an object weighs a kilogram", they really mean kilogram-force ( kg-f), which is about 9.8 times the kilogram-mass.Īlthough it is inconvenient, in scientific work you should refer to an object as kilogram-mass ( kg) and kilogram-weight ( kg-f) as the safest approach. However, most people do not use newtons for weight in everyday measurements. Weight is then the resulting force when a mass is accelerated by gravity, as stated in newtons. The official metric unit of force is the newton ( N), which is the force required to accelerate 1 kg-mass to 1 meter/second-squared. This can cause confusion when trying to make scientific calculations. Unfortunately, many people-and even some textbooks-state weight in terms of kilograms. A kilogram is defined as the SI or metric unit of mass.
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