ICSE Class 9 Answered
Need for measurements -In this video I didn't get the four points of - How to choose the units.Pls elaborate those four points.
Asked by muskaanabdullah71.9spicertl | 13 May, 2020, 06:33: PM
Expert Answer
The four characteristics of standard unit are: -
1. It must be of convenient size.
This means unit which we are using must be according to requirement.
For example: - If we are measuring the diameter of wire then the unit can be in millimetrebut if we are measuring the distance between the two cities then we cannot measure it in centimetres of millimetreseven if they are units of measuring length. So for measuring large distances between cities we will use kilometres.
2. There must not be ambiguity
This means the objective for the choice of unit must be clear and should not have inexactness.
While solving numerical, make sure that all the quantities are in same system of units.
While solving numerical, make sure that all the quantities are in same system of units.
For example:- While calculating density make sure that units of mass, volume and density is either in CGS system or in SI unit.
If you have to calculate the density in kg/m3 then mass must be converted in kilogram and volume to m3
3. It must be reproducible
There are many ways in which a physical quantity may be expressed.
The system of units was introduced to keep the expression of physical units uniform or less deviated.
These units are set in such a way that they remain reproducible so that they get easily converted.
Conversion (reproducibility) of units helps in maintaining the uniformity of the units for a concerned measurement or calculation.
This is the meaning and the reason why units should be reproducible.eg. 1Kg = 1000 g = 100000 mg.
4. Units must not change with space and time
4. Units must not change with space and time
It means units must not change from location to location and with change in time.
Thus, SI system is adopted everywhere to keep consistency.
Answered by Shiwani Sawant | 13 May, 2020, 07:28: PM
Concept Videos
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Measurements and Experimentation
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Measurements and Experimentation
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