# 0.4 1.5 physical quantities and units  (Page 3/17)

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## Metric prefixes

SI units are part of the metric system    . The metric system is convenient for scientific and engineering calculations because the units are categorized by factors of 10. [link] gives metric prefixes and symbols used to denote various factors of 10.

Metric systems have the advantage that conversions of units involve only powers of 10. There are 100 centimeters in a meter, 1000 meters in a kilometer, and so on. In nonmetric systems, such as the system of U.S. customary units, the relationships are not as simple—there are 12 inches in a foot, 5280 feet in a mile, and so on. Another advantage of the metric system is that the same unit can be used over extremely large ranges of values simply by using an appropriate metric prefix. For example, distances in meters are suitable in construction, while distances in kilometers are appropriate for air travel, and the tiny measure of nanometers are convenient in optical design. With the metric system there is no need to invent new units for particular applications.

The term order of magnitude    refers to the scale of a value expressed in the metric system. Each power of $\text{10}$ in the metric system represents a different order of magnitude. For example, ${\text{10}}^{1},\phantom{\rule{0.25em}{0ex}}{\text{10}}^{2},\phantom{\rule{0.25em}{0ex}}{\text{10}}^{3}$ , and so forth are all different orders of magnitude. All quantities that can be expressed as a product of a specific power of $\text{10}$ are said to be of the same order of magnitude. For example, the number $\text{800}$ can be written as $8×{\text{10}}^{2}$ , and the number $\text{450}$ can be written as $4.5×{\text{10}}^{2}.$ Thus, the numbers $\text{800}$ and $\text{450}$ are of the same order of magnitude: ${\text{10}}^{2}.$ Order of magnitude can be thought of as a ballpark estimate for the scale of a value. The diameter of an atom is on the order of while the diameter of the Sun is on the order of

Metric prefixes for powers of 10 and their symbols
Prefix Symbol Value See Appendix A for a discussion of powers of 10. Example (some are approximate)
exa E ${\text{10}}^{\text{18}}$ exameter Em distance light travels in a century
peta P ${\text{10}}^{\text{15}}$ petasecond Ps 30 million years
tera T ${\text{10}}^{\text{12}}$ terawatt TW powerful laser output
giga G ${\text{10}}^{9}$ gigahertz GHz a microwave frequency
mega M ${\text{10}}^{6}$ megacurie MCi high radioactivity
kilo k ${\text{10}}^{3}$ kilometer km about 6/10 mile
hecto h ${\text{10}}^{2}$ hectoliter hL 26 gallons
deka da ${\text{10}}^{1}$ dekagram dag teaspoon of butter
${\text{10}}^{0}$ (=1)
deci d ${\text{10}}^{-1}$ deciliter dL less than half a soda
centi c ${\text{10}}^{-2}$ centimeter cm fingertip thickness
milli m ${\text{10}}^{-3}$ millimeter mm flea at its shoulders
micro µ ${\text{10}}^{-6}$ micrometer µm detail in microscope
nano n ${\text{10}}^{-9}$ nanogram ng small speck of dust
pico p ${\text{10}}^{-\text{12}}$ picofarad pF small capacitor in radio
femto f ${\text{10}}^{-\text{15}}$ femtometer fm size of a proton
atto a ${\text{10}}^{-\text{18}}$ attosecond as time light crosses an atom

## Unit conversion and dimensional analysis

It is often necessary to convert from one type of unit to another. For example, if you are reading a European cookbook, some quantities may be expressed in units of liters and you need to convert them to cups. Or, perhaps you are reading walking directions from one location to another and you are interested in how many miles you will be walking. In this case, you will need to convert units of feet to miles.

#### Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Kinematics. OpenStax CNX. Sep 11, 2015 Download for free at https://legacy.cnx.org/content/col11878/1.5
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