Weight is a measurement of the force of gravity acting on an object and may be defined as the mass times the gravitational acceleration : w = mg.
In everyday parlance "weight" is often incorrectly used as a synonym for mass,but weight and mass are fundamentally different quantities: mass is an intrinsic property of matter, whereas weight is a force that results from the action of gravity on matter.Since the weight is a force, its SI unit is the newton.Mass SI unit is the kilogram.
The distinction between mass and weight on the surface of the Earth is unimportant for many practical purposes because the strength of gravity is roughly the same anywhere on the surface of the Earth. Under standard conditions on the Earth's surface 1 kilogram weighting 9.8 Newtons.
The SI unit of mass is kilogram and the SI unit of weight is newton.The SI is abbreviated from the French Système international d'unités(International System of Units).
A newton is the amount of force required to accelerate a body with a mass of one kilogram at a rate of one meter per second squared.
The kilogram is defined as the mass of the standard kilogram, a platinum-iridium bar in the custody of the BIPM near Paris, France. Copies of this bar are kept by the standards agencies of all the major industrial nations.One kilogram equals exactly 1000 grams , or about 2.204 622 6 pounds. By design, this is approximately the mass of a liter of water.
In some countries , including the United Kingdom and the United States, the governments have officially defined the pound as a unit of mass. The pound-force is still common in engineering and other applications; one pound of force being the weight force exerted by a one pound mass when the acceleration is equal to the standard acceleration of gravity.
In United States customary units, the pound can be either a unit of force or a unit of mass.Related units are the poundal and the slug. The poundal is defined as the force necessary to accelerate a one-pound object at 1 ft/s².The slug is defined as the amount of mass that accelerates at 1 ft/s² when a pound of force is exerted on it.
The use of the slug and poundal is discouraged, and the use of exclusively SI units for all scientific work is strongly encouraged.