> Understanding Measurement

Physics as a master mechanic-hydraulic-fluid mechanics, heavy equipment
measurements require very careful to symptoms
studied can be explained (and predictable) accurately. Actually
measurement is not only absolutely necessary for physics, but also for fields
other sciences, including the application of such knowledge. In other words, no
theory, principles, and laws in natural science that can be
accepted unless accompanied by the results of accurate measurements.

What is a measurement? To find out things
, consider the following descriptions: for example you with your friends
measured the length of the table with hand span. Results
measurements were performed using inch units. For example, if
use your hand span, then the result is the same length of table
with 25 inch arms.

However, if using inch units
your friend's hand so that the same long table with 23 inch arms.
The difference these results suggest that the measurement result depends
the units used. Thus the measurement is defined
as a process of comparing a quantity to other quantities
(A) used as a unit. The unit is comparable in
measurements.

In the above activities, which measure the length of the table that otherwise
with numbers, then the length of the scale. So everything
can be measured and expressed as the number or value is called scale.
For example, table length is 100 centimeters, the length is
scale with 100 as the value and centimeters as units, or
mass table was 20 kilograms, then the mass is the scale with 20
as the value and the kilogram as a unit. Magnitude is `something
can be measured and expressed as the number or value and has units.
The unit is comparable in the measurement.

The measurement is to compare something with something
Another is regarded as a benchmark. So in the measurement there are two
The main factor is the comparison and benchmark (standard). In our junior class 1
have studied the subject of measurement. Here we will only
repeat part of it, to refresh our understanding of
what's contained in the measurement.

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> Quantities and units

The properties of an object or event that we measured, for example
body length, body mass, the length of time running around a
field called the scale, what scale we can measure from a
book?

In a book, we can measure the mass, length, width, and
thick book. How do we express the results of measuring the length of the book?
For example, a book length equal to 25 inches; centimeters called
unit of length scale. The mass of books equal to 1 kilogram, kilograms
called the unit of mass scale. So always follow the scale unit,
never before him.

In our society there is sometimes
units that are not standard or non-standard, such as unit length
selected fathoms or span. The unit is not standard because it does not have
same size for different people. One inch of adult
another with one inch of the children. That is why the span and not depa
used as a standard unit of measurement physics.

Are the conditions that must be possessed of a unit that can be a unit
standard? Some of the main requirements are as follows:

1. Unit value should be fixed, either in hot or cold weather, for people
adults and for children, and to changes
other environments. For example, the span can not be used as a unit
default because different for each person, while
meter applies equally well to adults mapun children. By
therefore, the meter can be used as standard units.

2. Easily recoverable (easy to imitate), so that others who want to
use these units in measurement can
obtain it without much difficulty. Unit mass is kilogram,
easily be recovered by a comparison. Thus,
pounds can be used as standard units. Can we imagine,
how busy if a unit are difficult to make a replica so that the world
there is only one standard unit. Other people who want
measure the amount in question must use only
The standard units to obtain accurate results.

3. The unit must be internationally accepted. It deals with
interests of science and technology. By deterimanya a
unit as international units, the scientists from one country
can easily understand the measurement results from scientists in other countries.

Unit system most widely used around the world, which is valid
in interasional is the SI unit system, short for language
French Systeme International d'Unites. This system was proposed in the General
Conference on weights and Measures of the International Academy of
Science in 1960. In this unit system, there are seven scale
the so-called principal amount.

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> The amount of principal and derivative

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 º 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.

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