The amount of principal
The amount of principal is the amount that the unit has been defined prior
first. Seven basic quantities in the SI unit system are:
Length (meters)
Mass (kg)
Time (second)
Strong electric current (ampere)
Temperature (kelvin)
Light intensity (candela)
Amount of substance (mole)
Units such as meters, kilograms, and the second is already
defined first. What is the definition of units of
principal amount of these? In the following explanation will be presented definitions
of three basic quantities of length, mass, and time, while unit
Other quantities will be discussed when we discuss the subject
concerned with the amount of vine.
Long
The standard unit for length is the meter in the SI. System of units
based on the meter as a standard measurement system called
metric. At first, the meter is defined as one ten-millionth the distance
between equator and north pole of the earth is measured through the meridian
through the city of Paris. As a standard meter, was made a metal rod
platinum-iridium, which contained both ends of each stroke,
where the distance between two scratches are equal to 1 meter.
In 1960, a standard meter redefined as 1,650,763.73
times the wavelength in vacuum of the color spectrum
orange-red krypton-86 atoms. This is done to re-defining
increase the ease of a standard meter to be made replica, in addition to
to increase accuracy. However, even this definition does not re-
last long, only about 23 years. In 1983, one meter
defined as the distance traveled by light in vacuum during
1/299.792.458 second. With this last definition, complete meters as
standard units meet the requirements specified standard units in front.
Mass
The mass of an object is a number of substances contained in
an object. Mass units in the SI unit system is
kilogram. As a standard for the kilogram, the kilogram standard was made,
which is a metal cylinder made of platinum-iridium, which is now
This is stored in Sevres, near Paris. Initially one kilogram same
with a mass of 1000 cm ³ of pure water at a temperature where the density
maximum, which is 4 ยบ C. But mistakes happen, because it turns out one
kilogram exactly is 1000.028 cm ³ of water.
In everyday conversation, we often confuse the sense mix
mass with weight, but they are different. Weight is the amount of
force experienced by objects due to gravity on the object. For
daily use, is not a confusion of terms
problem, but in physics or an exact science, the definition of mass
and weight should really be distinguished. Has units of mass and weight
different, mass has units of kilograms, while the weight has
Newton unit. The main difference between mass and weight
is that the masses do not depend on the place where the object is located,
while the weight depending on where the object is located. So the weight change
according to the place.
Left
Standard units for time are seconds, which was originally defined
1/86.400 day as the sun. But when scientists found that
solar day is reduced about 0.001 seconds every century, then the second
1/86.400 redefined as solar day in 1900. In
1967, the second was redefined as the time interval from 9192631770
oscillation of the radiation generated by transitions in cesium-133 atom. Tool
measuring time using a cesium atom is cesium atomic clock, which
have a very high accuracy, ie during the 3000 year only
have a second mistake.
The amount of derivatives.
Most of the values which we use in physics and sciences
terapannya (including fluid mechanics and hydraulics, and heavy equipment)
units have a combination of units
principal amount. Such quantities, which determined its unit
based on the principal amount of units, called the scale derivative.
Examples
of the magnitude of this derivative is the area of a square area. Same broad
length times width, where length and width are both
unit length. So vast is the quantity derived from
length scale multiplication with a scale length. Example: Other:
speed (distance divided by time), pressure (force divided by area), the volume of beam
(Length x width x height), discharge (volume divided by time). We know that
speed is the distance (scale length) divided by time. So speed
is a derivative quantity obtained by dividing the amount of
long with the amount of time.
How unit quantities derived from them? It is clear
that the units for the amount of derivatives in accordance with how the
derived quantities were obtained from a combination of basic quantities.
Because the same large scale multiplication of two long, then the unit area
together with the multiplication of two units of length, namely meter x meter = meter
square = m². The unit for speed is the unit of length divided by unit
time, ie meters per second = m / s. It is clear here that that the units
derivative quantities that follow describe the scale derivative. Unit
speed is m / s, mean speed equal to the length (distance) divided
time. The unit for volume is m beam, means the volume is the length
times the length times the length. Density has the units kg / m³, mean mass
type is the mass divided by volume.
