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The measurement of mass is an important concept in physics. The related concepts like a standard unit of mass and weight help to understand the amount of matter in an object. Mass and weight are used in many calculations and physics concepts. Many times both terms are used together; however, there is a difference between the two. The mass is the characteristic feature of the matter and remains constant at all times. It can be defined as the amount of matter in an object. In other words, weight is the measure of the force of the body when force of gravity is applied. So, how is mass calculated?
Measurement of mass:
The mass of any body is measured using balance. The obscure mass is contrasted and is the estimation of the mass of an object. Further, mass is always different from weight as it remains constant with respect to location while weight changes its value.
The SI unit of mass is kilogram and represented as kg. It is the basic unit of measurement of mass and is nearly equal to the mass of 1,000 cubic cm of water. However, some disturbances were observed in the calculations of mass using water and then using the alloy bars. Hence, Planck’s constant remains an established measurement of mass.
It states that one joule is equal to one kilogram times metre squared per second squared. The value of Planck’ constant is 6.62607015 × 10−34 joule second. The other main units of mass include:
- Milligram or mg: 0.001 gram
- Decigram or dg: 0.1 gram
- Centigram or cg: 0.01 gram
- Gram or g: 1,000 milligrams
- Dekagram or dag: 10 grams
- Hectogram or hg: 100 grams
- Metric ton or t: 1,000 kilograms
- Kilogram or kg: 1,000 grams
The units for considering the smallest value of mass or excessive large values of mass are:
- Atomic mass: It is used when the mass of atoms and molecules can’t be calculated with existing units. It is calculated as 1/12th of the mass of the C-12 carbon atom.
- Ton: It is used for measuring excessive large masses. One ton equals 1,000kg.
Difference between mass and weight:
Weight is the measure of the gravitational pull acting on a body and is measured by balance. It depends on the mass of the object and acceleration due to gravity of the object. Hence, it can be summed up that the weight of the body is directly proportional to its mass. A quick difference between mass and weight is as below:
Sr. No. | Property | Mass | Weight |
1 | Null value | Since mass is the quantity of matter in any object, it can never be zero. | Weight can be zero when there is no gravitational pull acting on the object. Hence, weight becomes zero in space. |
2 | Scalar or Vector | Mass has magnitude and hence is a scalar quantity. | Weight has magnitude but has direction towards the centre of the earth. Hence, it is a vector quantity. |
3 | Variations | There is no change in the mass of an object irrespective of its location. | The weight of an object changes with respect to its location. |
4 | Measurement | It is easy to measure mass using any ordinary balance. | Weight can be measured using a spring balance only. |
5 | Units | The units of mass include kilograms, grams, etc. | The unit of mass is Newton. |
Relation between mass and weight:
After having details about the key differences between mass and weight, the measurement of mass is incomplete without an established relation between these two.
It is established with the help of Newton’s second law that states that a free falling object has an acceleration “g” as the magnitude. Hence, if an object with 1 kg mass falls with an acceleration of 9.8 m/s2, the force experienced by it is:
F= ma
= (1kg) x (9.8m.s-2)
= (9.8 kg.m.s-2)
= 9.8N
Hence, a 1kg mass will have the weight of 9.8N.
Conclusion:
In this article, we learned about measurement of mass. SI unit of mass is ‘kg’. It is the basic unit of measurement of mass and is nearly equal to the mass of 1,000 cubic cm of water. Mass has only magnitude so it is a scalar quantity. Weight is the measure of the gravitational pull acting on a body and is measured by balance. Weight has magnitude and has direction towards the centre of the earth. Hence, it is a vector quantity.
