Measures
Measurement
is the process of attaching a numeric value to an aspect of natural phenomenon,such as the volume of the milk produced by a goat To begin the process of measurement, we need to recognize the type of phenomenon, called the physical dimension that we would like to measure. For example, the diameter of the front wheel of a bicycle is of type Length, how fast the bicycle is moving is described by Speed and the amount of air crammed inside the wheel is determined by Pressure (4)[1].
Standardization of measurement units
Measurements are most commonly made in the SI system, which contains seven fundamental units[2]: kilogram, meter, can deal, second, ampere, Kelvin, and mole.
These units are cited in the table below, which serves as a standard.
Base quantity | Base.unit | symbol | Current SI constants |
Time | Second | S | Hyperfine splitting in Cesium-133 |
Length | Meter | M | Speed of light in vacuum, c |
Mass | Kilogram | Kg | Mass of international prototype kilogram (IPK) |
Electric current | Ampere | A | Permeability of free space, permittivity of free space |
Temperature | Kelvin | K | Triple point of water, absolute zero |
Amount substance | Mole | Mol | Molar mass of carbon -12 |
Luminous intensity | Candela | Cd | Luminous efficacy of 540 THz source |
Note :
Other units can use in measurements such us:
a/- Length: the distance from one end of something to the other end: a measurement of how long something is.The units are: meter, centimeter, pond, inch......
b/- Surface: a surface is a set of points on which it is possible to identify locally using two real coordinates ,as in the plane (with x and y coordinates). Theunitism2orcm2......
c/- Volume: the volume, physical science or mathematics, is a quantity that measures the extension of an object or part of the space.The volume unit is M3,L
d/- Power: We can define power as the rate of doing work, it is the work done in unit time.The SI unit of power is Watt (W) which is joules per second (J/s). Sometimes the power of motor vehicles and other machines is given in terms of Horse power (hp),which is approximately equal to 745.7 watts .
