The System Unit
The system unit is a case that houses the electronic components of the computer used to process data. Although many system units resemble a box, they are available in many shapes and sizes. The case of the of the system unit, sometimes called a chassis, is made of metal or plastic and protects the internal electronic components from damage. All computes have a system unit (Alvarez 102). Components of the system unit include the processor, memory modules, adapter cards, drive bays, power supply, ports, and connectors. The processor interprets and carries out the basic instructions that operate a computer. A memory module houses memory chips. An adapter card is a circuit board that provides connections and functions not built into the motherboard. A drive bay holds a disk drive. The power supply allows electricity to travel into a computer. On a personal computer, the electronic components and most storage devices reside in the system unit. Other devices, such as a keyboard, mouse, microphone, monitor, printer, speakers, scanner, and digital camera, normally occupy space outside the system unit (How to Use a Computer). On a desktop personal computer, the system unit usually is a device separate from the monitor and keyboard. Some system units sit on top of a desk. Other models, called tower models, can stand vertically on the floor. To conserve space, an all-in-one computer houses the system unit in the same physical case as the monitor. On notebook computers, the keyboard and pointing device often occupy the same area on the top of the system unit. The display attaches to the system unit by hinges. The system unit on a PDA 9personal digital assistant) or hand held computer usually consume the entire device. On these small mobile devices, the display is part of the system unit, too.

Works Cited
Alvarez, Juan. Understanding Computer Basics: Stepping Toward Literacy. Chicago: Martin Publishing, 2005. How to Use a Computer, Shelly Cashman...

...The Metric system
Have you ever looked at the back of a food item or drink to check nutritional values? Everything on the label is measured in the metric system. Do you actually know how much sugar you are getting? Or how much of a certain medication you can safely take? Have you ever thought that there should be ten inches in a foot, ten feet in a yard? A system with a standard that makes sense. Well you’re in luck with the metricsystem.
The English Imperial system may be more familiar and comfortable for Americans, but it is still confusing to them because it has no standard. There are twelve inches in a foot, three feet in a yard, 5,280 feet in a mile. This is a system based on arbitrary rules, rules which make conversion of units clumsy and awkward for its users.
Have you ever had to Google how many fluid ounces are in a cup when cooking? Or stop to do math in your mind to determine how much you'll pay to put in new flooring in a room when you know its square footage but the materials are sold per square yard? I am sure that I'm not the only person that has a conversion app on their phone for just such occasions. As if our confusing system weren't enough on its own, we are surrounded by sort of a dual system. The metric system reigns in science, business (for international trade), and the military, because it is both more...

...Units of Measurement: Sections 1.4-1.5
Physical Quality Name of Unit Abbreviation
Mass Kilogram Kg
Length Meter m
Time Second sª (Sec)
Temperature Kelvin K
Amount of Substance Mole mol
• Système International d’Unitès (used in the science community world wide)
• Uses different base unit for quantity
Velocity m/s (two base units build velocity = derived unit) {g/sec, kg/min}
Metric System
Prefix Abbreviation Meaning
Mega M 106
Kilo k 103
Centi c 10-2
Milli m 10-3
Micro µ 10-6
Nano n 10-9
Pico p 10-12
Volume
Most common used metric u nits for volume: Liter (L), milliliter (mL),
1dm3 = 1L A liter is a cube 1 dm long on each side
1cm3 = 1mL A milliliter is a cube 1 cm long on each side
Uncertainty in Measurements
Different measuring devices have different uses and degrees of accuracy. Some examples are of these devices are:
• Graduated Cylinders
• Syringe
• Buret
• Pipet
• Volumetric Flask
Temperature
Measure of average kinetic energy of particles in a sample
• Kelvic Scale (purely scientific)
• Celsius Scale (scientific)
• Farenheit Scale (U.S. Only)
Molecules and atoms become unstable at Absolute zero.
No negative temperatures of Kelvins
Celsius scale is based on properties of water
0° is the freezing point of water
The Kelvin...

...Section 1.4—Converting Units
Often, a measurement is more convenient in one unit but is needed in another unit for calculations.
Dimensional Analysis is a method for converting between units.
Equivalents
Dimensional Analysis uses equivalents.
What is an equivalent?
Two measurements that have the same meaning. Ex:
What happens if you put one over the top of the other?
See your reference sheet for some common equivalencies.
We can use these conversion factors to switch between units! This “switching units stuff” is called Dimensional Analysis! The method I teach you today is important, I know there might be an easier way to you, but you need to trust me and go with it!
Dimensional Analysis
Dimensional analysis is based on using units to analyze how we solve a problem. We use the equivalents to show that two answers have the same meaning but they can be expressed in different ways.
27 inches –Can you figure out how many feet?
Before we teach you Unit Analysis we must understand Canceling!
27 inches x __1 foot___
12 inches
Anything that is on the top and the bottom of an expression will cancel
When canceling units…just cancel the units and NOT the numbers. (unless the numbers cancel out as well)
Steps for using Dimensional...

...
---TERMINOLOGY
Learn these basic pharmacology terms:
tolerance
synergism
antagonism
therapeutic
prophylactic
---METRIC CONVERSIONS
Here are some important tips to remember when converting from one metric unit to another … [mg]-to-[grams], [liters]-to-[ml], [cm]-to-[mm], etc …
1) First thing to ask yourself is … “what is the relationship between the two different units?”
Here is an example of what I mean. If you are asked to convert 300mg into its equivalent value expressed in grams (g), you first need to determine how many of the smaller units are contained in one of the larger units … in this case we would use the fact that [1g] is equal to [1000mg], or stated another way, each 1-gram contains 1000mg.
2) Knowing the relationship between units in a conversion gives you a critical piece of info that you will need to solve the problem. This piece of info is called a RATIO. IMPORTANT NOTE: a RATIO can be inverted depending on what unit you are solving for. This is explained further in step-3 below.
3) The fact that one-gram equals 1000-mg can be expressed as a RATIO in either of the following two ways: [1g/1000mg] or [1000mg/1g]. You’ll see how valuable this ‘RATIO’ is in step-5 below where I will show you how to set-up this problem.
4) Using the numbers from above, here is what we know so far. We have our original value of 300mg, and we know that there are...

...Metric System
The metric system is a measuring system based on the increments of ten. The United States uses the customary system which is based on a completely different set of standards. Although some individuals might disagree, the United States should switch to the metric system because some of the United States already uses the metric system, the rest of the world uses the metricsystem, and the measurements of items intended for use world-wide are presented in the metric system. Thus, the United States should convert from the customary system to the metric system.
First of all, some of the United States already uses the metric system. Our stock market is set up on the decimal system like the metric system, and many products seem to have their quantities determined for the metric system. For example, a bottle of Lipton ice tea contains 500 milliliters and 16.9 ounces. This shows Lipton uses the metric system and only accommodates the United States’ customary system because the capacity is an even number for the metric system, but an irregular number for the customary system. The United States also uses the metric system for pharmaceutical drugs. Each pill or dosage is measured is either milligrams...

...Newtonian Mechanics 8.01
Units and Dimensional Analysis
1
Dimensions in Mechanics
Physical quantities have dimensions. These quantities are the basic dimensions: - mass, length, time with dimension symbols M, L, T
Other quantities’ dimensions are more complex:
- [velocity] = length/time = LT-1 - [force] = (mass)(length) /(time)2 = MLT-2 - [any mechanical quantity] = Ma Lb Tc where a b, and c can be negative and/or non-integer
2
Base Quantities
Name Length Time Mass Electric current Thermodynamic Temperature Amount of substance Luminous intensity Symbol for quantity l t m I T n IV Symbol for dimension L T M I Θ N J SI base unit meter second kilogram ampere kelvin mole candela 3
SI Base Units:
Second: The second (s) is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. Meter: The meter (m) is now defined as the distance traveled by a light wave in vacuum in 1/299,792,458 seconds. Mass: The SI standard of mass is a platinum-iridium cylinder assigned a mass of 1 kg
Image courtesy of the National Bureau of Standards
4
Speed of Light
In 1983 the General Conference on Weights and Measures defined the speed of light to be the best measured value at that time:
c = 299, 792, 458 meters/second
This had the effect that length became a derived quantity, but the meter was kept around for...

...Ggggggggg, Aaaaaaaa
“Draft 2”
W 310
The United States and the Metric System
The issue of whether the United States should change to the metric, a decimal-based system of measurement units, has been widely debated in our community for a long time. No one decided the United States should go metric, so the traditional system of weights and measures is still not used in by the goverment. However, it is an important issue because the metric system has become widespread throughout the United States’ economy. Consumers may be surprised at the number of items in everyday use that have been manufactured in metric units for some time. For example, the metric system for automobiles, computers, wine, and soft drinks has been accepted with little difficulty. In addition, American scientific and medical communities use metric units almost exclusively. I strongly believe that the metric system is imperative to maintain America’s competitive edge in the global economy for some very compelling reasons.
First of all, the United States should switch to the metric system because this system is easy to use and learn. The United States doesn’t have a perfectly good measuring system. We have a clumsy, entangled, confusing measuring system that confuses not only the rest of the world, but it...

...The Metric System
Scientific data is always reported using metric systemunits of measurement. There are four basic metric measurement units:
• Length = meter (m)
• Volume = liter (l)
• Mass (weight) = gram (g)
• Temperature = ° Celsius (° C)
All four metric system basic units can be converted into larger or smaller units simply by adding a prefix in front of the basic unit:
Unit prefixes:
• kilo (k) = Makes the basic unit 1000 times larger (103)
• deci (d) = Makes the basic unit 10 time smaller (10-1 or 1/10)
• centi (c) = Makes the basic unit 100 times smaller (10-2 or 1/100)
• milli (m) = Makes the basic unit 1000 times smaller (10-3 or
1/1000)
• micro (µ) = Makes the basic unit a million times smaller (10-6 or
1/1,000,000)
For example, a person might weigh 63,000 grams. That same person also weighs 63 kilograms (kg) since each kilogram is equal to 1000 grams.
These larger and smaller units are called “derived” units
A) Length
The basic unit of length in the metric system is the meter (m). Common derived units are the centimeter (cm) (10-2 or 1/100 of a meter) and the millimeter (mm) (10-3 or 1/1000 of a meter). For measuring large distances, the kilometer...