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1.2 Physical quantities and units  (Page 4/18)

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Metric prefixes for powers of 10 and their symbols
Prefix Symbol Value See [link] for a discussion of powers of 10. Example (some are approximate)
exa E 10 18 size 12{"10" rSup { size 8{"18"} } } {} exameter Em 10 18  m size 12{"10" rSup { size 8{"18"} } " m"} {} distance light travels in a century
peta P 10 15 size 12{"10" rSup { size 8{"15"} } } {} petasecond Ps 10 15  s size 12{"10" rSup { size 8{"15"} } " s"} {} 30 million years
tera T 10 12 size 12{"10" rSup { size 8{"12"} } } {} terawatt TW 10 12  W size 12{"10" rSup { size 8{"12"} } `W} {} powerful laser output
giga G 10 9 size 12{"10" rSup { size 8{9} } } {} gigahertz GHz 10 9  Hz size 12{"10" rSup { size 8{9} } `"Hz"} {} a microwave frequency
mega M 10 6 size 12{"10" rSup { size 8{6} } } {} megacurie MCi 10 6  Ci size 12{"10" rSup { size 8{6} } `"Ci"} {} high radioactivity
kilo k 10 3 size 12{"10" rSup { size 8{3} } } {} kilometer km 10 3  m size 12{"10" rSup { size 8{3} } " m"} {} about 6/10 mile
hecto h 10 2 size 12{"10" rSup { size 8{2} } } {} hectoliter hL 10 2  L size 12{"10" rSup { size 8{2} } " L"} {} 26 gallons
deka da 10 1 size 12{"10" rSup { size 8{1} } } {} dekagram dag 10 1  g size 12{"10" rSup { size 8{1} } `g} {} teaspoon of butter
— — 10 0 size 12{"10" rSup { size 8{0} } } {} (=1)
deci d 10 − 1 size 12{"10" rSup { size 8{ - 1} } } {} deciliter dL 10 − 1  L size 12{"10" rSup { size 8{ - 1} } `L} {} less than half a soda
centi c 10 − 2 size 12{"10" rSup { size 8{ - 2} } } {} centimeter cm 10 − 2  m size 12{"10" rSup { size 8{ - 2} } `m} {} fingertip thickness
milli m 10 − 3 size 12{"10" rSup { size 8{ - 3} } } {} millimeter mm 10 − 3  m size 12{"10" rSup { size 8{ - 3} } `m} {} flea at its shoulders
micro µ 10 − 6 size 12{"10" rSup { size 8{ - 6} } } {} micrometer µm 10 − 6  m size 12{"10" rSup { size 8{ - 6} } `m} {} detail in microscope
nano n 10 − 9 size 12{"10" rSup { size 8{ - 9} } } {} nanogram ng 10 − 9  g size 12{"10" rSup { size 8{ - 9} } `g} {} small speck of dust
pico p 10 − 12 size 12{"10" rSup { size 8{ - "12"} } } {} picofarad pF 10 − 12  F size 12{"10" rSup { size 8{ - "12"} } F} {} small capacitor in radio
femto f 10 − 15 size 12{"10" rSup { size 8{ - "15"} } } {} femtometer fm 10 − 15  m size 12{"10" rSup { size 8{ - "15"} } `m} {} size of a proton
atto a 10 − 18 size 12{"10" rSup { size 8{ - "18"} } } {} attosecond as 10 − 18  s size 12{"10" rSup { size 8{ - "18"} } `s} {} time light crosses an atom

Known ranges of length, mass, and time

The vastness of the universe and the breadth over which physics applies are illustrated by the wide range of examples of known lengths, masses, and times in [link] . Examination of this table will give you some feeling for the range of possible topics and numerical values. (See [link] and [link] .)

A magnified image of tiny phytoplankton swimming among the crystal of ice.[
Tiny phytoplankton swims among crystals of ice in the Antarctic Sea. They range from a few micrometers to as much as 2 millimeters in length. (credit: Prof. Gordon T. Taylor, Stony Brook University; NOAA Corps Collections)
A view of Abell Galaxy with some bright stars and some hot gases.
Galaxies collide 2.4 billion light years away from Earth. The tremendous range of observable phenomena in nature challenges the imagination. (credit: NASA/CXC/UVic./A. Mahdavi et al. Optical/lensing: CFHT/UVic./H. Hoekstra et al.)

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.

Let us consider a simple example of how to convert units. Let us say that we want to convert 80 meters (m) to kilometers (km).

The first thing to do is to list the units that you have and the units that you want to convert to. In this case, we have units in meters and we want to convert to kilometers .

Next, we need to determine a conversion factor    relating meters to kilometers. A conversion factor is a ratio expressing how many of one unit are equal to another unit. For example, there are 12 inches in 1 foot, 100 centimeters in 1 meter, 60 seconds in 1 minute, and so on. In this case, we know that there are 1,000 meters in 1 kilometer.

Now we can set up our unit conversion. We will write the units that we have and then multiply them by the conversion factor so that the units cancel out, as shown:

80 m × 1 km 1000 m = 0 .080 km. size 12{"80"" m" times { {"1 km"} over {"1000 m"} } =0 "." "080"`"km"} {}

Note that the unwanted m unit cancels, leaving only the desired km unit. You can use this method to convert between any types of unit.

Questions & Answers

how does the planets on our solar system orbit
cheten Reply
how many Messier objects are there in space
satish Reply
did you g8ve certificate
Richard Reply
what are astronomy
Issan Reply
Astronomy (from Ancient Greek ἀστρονομία (astronomía) 'science that studies the laws of the stars') is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution.
Rafael
vjuvu
Elgoog
what is big bang theory?
Rosemary
what type of activity astronomer do?
Rosemary
No
Richard
the big bang theory is a theory which states that all matter was compressed together in one place the matter got so unstable it exploded releasing All its contents in the form of hydrogen
Roaul
I want to be an astronomer. That's my dream
Astrit
Who named the the whole galaxy?
Shola Reply
solar Univers
GPOWER
what is space
Richard
what is the dark matter
Richard
what are the factors upon which the atmosphere is stratified
Nicholas Reply
is the big bang the sun
Folakemi Reply
no
Sokak
bigbang is the beginning of the universe
Sokak
but thats just a theory
Sokak
nothing will happen, don't worry brother.
Vansh
what does comet means
GANGAIN Reply
these are Rocky substances between mars and jupiter
GANGAIN
Comets are cosmic snowballs of frozen gases , rock and dust that orbit the sun. They are mostly found between the orbits of Venus and Mercury.
Aarya
hllo
John
hi
John
qt rrt
John
r u there
John
hey can anyone guide me abt international astronomy olympiad
sahil
how can we learn right and true ?
Govinda Reply
why the moon is always appear in an elliptical shape
Gatjuol Reply
Because when astroid hit the Earth then a piece of elliptical shape of the earth was separated which is now called moon.
Hemen
what's see level?
lidiya Reply
Did you mean eye sight or sea level
Minal
oh sorry it's sea level
lidiya
according to the theory of astronomers why the moon is always appear in an elliptical orbit?
Gatjuol
hi !!! I am new in astronomy.... I have so many questions in mind .... all of scientists of the word they just give opinion only. but they never think true or false ... i respect all of them... I believes whole universe depending on true ...থিউরি
Govinda
hello
Jackson
hi
Elyana
we're all stars and galaxies a part of sun. how can science prove thx with respect old ancient times picture or books..or anything with respect to present time .but we r a part of that universe
Reply
w astronomy and cosmology!
Michele
another theory of universe except big ban
Albash Reply
how was universe born
Asmit Reply
there many theory to born universe but what is the reality of big bang theory to born universe
Asmit
what is the exact value of π?
Nagalakshmi
by big bang
universal
there are many theories regarding this it's on you believe any theory that you think is true ex. eternal inflation theory, oscillation model theory, multiple universe theory the big bang theory etc.
Aarya
I think after Big Bang!
Michele
from where on earth could u observe all the stars during the during the course of an year
Karuna Reply
I think it couldn't possible on earth
Nagalakshmi
in this time i don't Know
Michele
is that so. the question was in the end of this chapter
Karuna
in theory, you could see them all from the equator (though over the course of a year, not at pne time). stars are measured in "declination", which is how far N or S of the equator (90* to -90*). Polaris is the North star, and is ALMOST 90* (+89*). So it would just barely creep over the horizon.
Christopher
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Source:  OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
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