# 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 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

## 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] .)

## 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:

$80\overline{)\text{m}}×\frac{\text{1 km}}{1000\overline{)\text{m}}}=0\text{.080 km.}$

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.

how many subject is in physics
the write question should be " How many Topics are in O- Level Physics, or other branches of physics.
effiom
how many topic are in physics
Praise
yh I need someone to explain something im tryna solve . I'll send the question if u down for it
a ripple tank experiment a vibrating plane is used to generate wrinkles in the water .if the distance between two successive point is 3.5cm and the wave travel a distance of 31.5cm find the frequency of the vibration
Tamdy
the range of objects and phenomena studied in physics is
what is Linear motion
straight line motion is called linear motion
then what
Amera
linear motion is a motion in a line, be it in a straight line or in a non straight line. It is the rate of change of distance.
Saeedul
Hi
aliyu
Richard
Linear motion is a one-dimensional motion along a straight line, and can therefore be described mathematically using only one spatial dimension
Jason
is a one-dimensional motion along a straight line, and can therefore be described mathematically using only one spatial dimensions.
Praise
what is a classical electrodynamics?
Marga
what is dynamics
Marga
dynamic is the force that stimulates change or progress within the system or process
Oze
what is the formula to calculate wavelength of the incident light
if a spring is is stiffness of 950nm-1 what work will be done in extending the spring by 60mmp
State the forms of energy
machanical
Ridwan
Word : Mechanical wave Definition : The waves, which need a material medium for their propagation, e.g., Sound waves. \n\nOther Definition: The waves, which need a material medium for their propagation, are called mechanical waves. Mechanical waves are also called elastic waves. Sound waves, water waves are examples of mechanical waves.t Definition: wave consisting of periodic motion of matter; e.g. sound wave or water wave as opposed to electromagnetic wave.h
correct
Akinpelu
what is mechanical wave
a wave which require material medium for its propagation
syed
The S.I unit for power is what?
watt
Okoli
Am I correct
Okoli
it can be in kilowatt, megawatt and so
Femi
yes
Femi
correct
Jaheim
kW
Akinpelu
OK that's right
Samuel
SI.unit of power is.watt=j/c.but kw.and Mw are bigger.umots
syed
What is physics
study of matter and its nature
Akinpelu
The word physics comes from a Greek word Physicos which means Nature.The Knowledge of Nature. It is branch of science which deals with the matter and energy and interaction between them.
Uniform
why in circular motion, a tangential acceleration can change the magnitude of the velocity but not its direction
reasonable
Femi
because it is balanced by the inward acceleration otherwise known as centripetal acceleration
MUSTAPHA
What is a wave
Tramsmission of energy through a media
Mateo
is the disturbance that carry materials as propagation from one medium to another
Akinpelu
mistakes thanks
Akinpelu
find the triple product of (A*B).C given that A =i + 4j, B=2i - 3j and C = i + k
Difference between north seeking pole and south seeking pole