# 0.4 1.5 physical quantities and units  (Page 4/17)

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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.

Click [link] for a more complete list of conversion factors.

Approximate values of length, mass, and time
Lengths in meters Masses in kilograms (more precise values in parentheses) Times in seconds (more precise values in parentheses)
${\text{10}}^{-\text{18}}$ Present experimental limit to smallest observable detail ${\text{10}}^{-\text{30}}$ Mass of an electron ${\text{10}}^{-\text{23}}$ Time for light to cross a proton
${\text{10}}^{-\text{15}}$ Diameter of a proton ${\text{10}}^{-\text{27}}$ Mass of a hydrogen atom ${\text{10}}^{-\text{22}}$ Mean life of an extremely unstable nucleus
${\text{10}}^{-\text{14}}$ Diameter of a uranium nucleus ${\text{10}}^{-\text{15}}$ Mass of a bacterium ${\text{10}}^{-\text{15}}$ Time for one oscillation of visible light
${\text{10}}^{-\text{10}}$ Diameter of a hydrogen atom ${\text{10}}^{-5}$ Mass of a mosquito ${\text{10}}^{-\text{13}}$ Time for one vibration of an atom in a solid
${\text{10}}^{-8}$ Thickness of membranes in cells of living organisms ${\text{10}}^{-2}$ Mass of a hummingbird ${\text{10}}^{-8}$ Time for one oscillation of an FM radio wave
${\text{10}}^{-6}$ Wavelength of visible light $\text{1}$ Mass of a liter of water (about a quart) ${\text{10}}^{-3}$ Duration of a nerve impulse
${\text{10}}^{-3}$ Size of a grain of sand ${\text{10}}^{2}$ Mass of a person $\text{1}$ Time for one heartbeat
$\text{1}$ Height of a 4-year-old child ${\text{10}}^{3}$ Mass of a car ${\text{10}}^{5}$ One day $\left(8\text{.}\text{64}×{\text{10}}^{4}\phantom{\rule{0.25em}{0ex}}\text{s}\right)$
${\text{10}}^{2}$ Length of a football field ${\text{10}}^{8}$ Mass of a large ship ${\text{10}}^{7}$ One year (y) $\left(3\text{.}\text{16}×{\text{10}}^{7}\phantom{\rule{0.25em}{0ex}}\text{s}\right)$
${\text{10}}^{4}$ Greatest ocean depth ${\text{10}}^{\text{12}}$ Mass of a large iceberg ${\text{10}}^{9}$ About half the life expectancy of a human
${\text{10}}^{7}$ Diameter of the Earth ${\text{10}}^{\text{15}}$ Mass of the nucleus of a comet ${\text{10}}^{\text{11}}$ Recorded history
${\text{10}}^{\text{11}}$ Distance from the Earth to the Sun ${\text{10}}^{\text{23}}$ Mass of the Moon ${\text{10}}^{\text{17}}$ Age of the Earth
${\text{10}}^{\text{16}}$ Distance traveled by light in 1 year (a light year) ${\text{10}}^{\text{25}}$ Mass of the Earth ${\text{10}}^{\text{18}}$ Age of the universe
${\text{10}}^{\text{21}}$ Diameter of the Milky Way galaxy ${\text{10}}^{\text{30}}$ Mass of the Sun
${\text{10}}^{\text{22}}$ Distance from the Earth to the nearest large galaxy (Andromeda) ${\text{10}}^{\text{42}}$ Mass of the Milky Way galaxy (current upper limit)
${\text{10}}^{\text{26}}$ Distance from the Earth to the edges of the known universe ${\text{10}}^{\text{53}}$ Mass of the known universe (current upper limit)

## Unit conversions: a short drive home

Suppose that you drive the 10.0 km from your university to home in 20.0 min. Calculate your average speed (a) in kilometers per hour (km/h) and (b) in meters per second (m/s). (Note: Average speed is distance traveled divided by time of travel.)

what is variations in raman spectra for nanomaterials
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
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
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?
what is a peer
What is meant by 'nano scale'?
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 ?
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?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
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?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
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?
absolutely yes
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
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