# 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 ${\text{10}}^{\text{18}}$ 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.

Determine the total force and the absolute pressure on the bottom of a swimming pool 28.0m by 8.5m whose uniform depth is 1 .8m.
for the answer to complete, the units need specified why
That's just how the AP grades. Otherwise, you could be talking about m/s when the answer requires m/s^2. They need to know what you are referring to.
Kyle
Suppose a speck of dust in an electrostatic precipitator has 1.0000×1012 protons in it and has a net charge of –5.00 nC (a very large charge for a small speck). How many electrons does it have?
how would I work this problem
Alexia
how can you have not an integer number of protons? If, on the other hand it supposed to be 1e12, then 1.6e-19C/proton • 1e12 protons=1.6e-7 C is the charge of the protons in the speck, so the difference between this and 5e-9C is made up by electrons
Igor
what is angular velocity
Why does earth exert only a tiny downward pull?
hello
Islam
Why is light bright?
an 8.0 capacitor is connected by to the terminals of 60Hz whoes rms voltage is 150v. a.find the capacity reactance and rms to the circuit
thanks so much. i undersooth well
what is physics
is the study of matter in relation to energy
Kintu
a submersible pump is dropped a borehole and hits the level of water at the bottom of the borehole 5 seconds later.determine the level of water in the borehole
what is power?
power P = Work done per second W/ t. It means the more power, the stronger machine
Sphere
e.g. heart Uses 2 W per beat.
Rohit
A spherica, concave shaving mirror has a radius of curvature of 32 cm .what is the magnification of a persons face. when it is 12cm to the left of the vertex of the mirror
did you solve?
Shii
1.75cm
Ridwan
my name is Abu m.konnek I am a student of a electrical engineer and I want you to help me
Abu
the magnification k = f/(f-d) with focus f = R/2 =16 cm; d =12 cm k = 16/4 =4
Sphere
what do we call velocity
Kings
A weather vane is some sort of directional arrow parallel to the ground that may rotate freely in a horizontal plane. A typical weather vane has a large cross-sectional area perpendicular to the direction the arrow is pointing, like a “One Way” street sign. The purpose of the weather vane is to indicate the direction of the wind. As wind blows pa
hi
Godfred
Godfred
If a prism is fully imersed in water then the ray of light will normally dispersed or their is any difference?
the same behavior thru the prism out or in water bud abbot
Ju
If this will experimented with a hollow(vaccum) prism in water then what will be result ?
Anurag