Measurement of Mass

Measurement of Mass

Mass as a physical property of a body. Mass is a measure which helps in analysing how strong is a mutual attraction between two bodies. It is generally a wrong belief that mass is same as weight, as mass is a constant quantity, whereas weight is a variable quantity.

Mass: Mass is a basic characteristic of matter. It is independent of temperature, pressure or position of an object in space. Mass is expressed in different measures, but its standard unit is kilogram or kg. The SI or Standard Unit is issued by Bureau of Weights and Measures (BIPM). Its prototype is available in many laboratories across the world in India, National Physical Laboratory in New Delhi operates the Standard Unit as suggested by BIPM.

The unit of measuring mass is always chosen convenience wise, It means if we want to weigh a large animal, we would prefer kilogram as the unit and if we want to weigh small size animal, we may switch to another convenient unit. When it comes to measuring mass at the microscopic level, a standard unit of mass called “Unified Atomic Mass” is chosen.

Atomic Mass Unit: For extremely small and larger objects we use other units:

  • Tonne (Metric Ton) is equal to 1000 kg.
  • The Atomic Mass Unitis used while dealing with atoms and molecules whose masses are so small that the kilogram becomes inconvenient. One atomic mass unit is defined as 1/12th the mass of a Carbon-12 atom. The value of 1 atomic mass unit is obtained as 1.66 x 10⁻²⁷.

Measurement of Mass: Measurement of mass is most commonly done by a Balance. The unknown mass of a body is compared with a known value of mass. We obtain the value of an unknown mass in terms of a known value of mass. A balance works in space and in places of no gravity as well since changes in gravity affect both the masses on the balance equally.

What is Weight?

Mass is not the same as weight. While mass is the intrinsic property of the body, weight is the measure of the force exerted on the mass of the body due to gravity. Mass refers to a universal value of the object whereas weight is a localized interpretation of mass of the object. Weight is the effect of gravity and therefore we describe weight with the formula:

W = mg


m = Mass,

g = Acceleration due to gravity at that particular location.