Unit Conversion:
I do understand that with smart phones and computers you can find an online converter for almost anything these days. The reason I want you to learn how to do unit conversion by hand and in stages is that it helps illuminate otherwise hidden features of the question or problem we're trying to resolve. I'm not really that interested the answer for it's own sake but rather the thinking process that gets us there.
An important driver for this discussion is the recognition that numbers by themselves tell us very little about the world. 7 is a lovely number but until we know whether we're talking 7 dollars or 7 free lunches or 7 M$ there's not a lot of meaning. Because different industries and researcher tend to use different units (language really) in their area we often need to be able to convert those quantities into something that allows us to make meaningful comparisons.
We will be talking a lot about oil this term but oil is usually measured in gallons or barrels and electrical energy is usually measured in kWh. Until we express things in the same units it's very hard to figure out whats going on.
Because we are almost the last country in the world using 'English' units (not even the Brits use 'English' units!!!) we will use scientific units (metric or International System (SI)) exclusively. This will take some getting used to but it is the only way to catch up with everyone else. What are metric units? [ s, m, km, kg]
The Process:
The basic idea in unit conversion is to take what you have and multiply it by 1. This leaves the original item unchanged. When you divide any two things which are equivalent you have a fraction which represents 1. 60 s/1 min = 1 because 60 s and 1 min are different ways of saying the same thing. If I want to find the number of minutes in 30 days I start by writing down my starting point and where I want to get....
At each step in the process we are just multiplying the previous values by 1 which leaves the meaning unchanged but expresses the quantity of interest in new units. At each step we check to see if the units I want to replace cancel appropriately and whether I seem to be moving closer to my goal.
I am aware that this seems like a lot of steps and math for something I can look up on Google but as I said before I'm less concerned with the result than your understanding that there is a process that allows us to methodically work our way towards an answer.
Another quantity we'll be interested in is how much land is there for each person in Deschutes, Crook, or Jefferson county if we divided it up equally? Why do you think this might be important? Consider how much land is available to generate electricity from sunshine for the people who live here?
We'll often need to know the number of hours in a year in this course. When we are done with this activity write this number down in a place where you can access it easily when we need it in the future.
Activity: Using the process that has been illustrated determine the number of hours in a year.
Another quantity we'll be interested in is what each person's share of Deschutes, Crook, or Jefferson county is if we see the land as a form of community resource. Here are the links to the relevant information. In order to make effective comparisons with other communities around the world we need to express this number in m2/person.
Here is data that you might need:
Activity: Using the process that has been illustrated to determine each person's individual share of Jefferson County (as of the last census in 2010).
HW: Unit Conversion
Determine each person's individual share of Deschutes County from the data.
Activity: How many hours is a person-year? This is 1 person working 40 hrs each week for 1 year.
How much to I make if I work full time for 1 year making $5/hr? What does this tell you about the impact of a $5/hr raise at work? Want is the annual salary of someone who works full time for $20/hr?
In this class we will work with large numbers often because we are talking about energy use both at the country level and the personal level. To help make sense of the large numbers one strategy is to figure out what a billion of something is. One collection of a billion things that is often helpful is the number of years that is equivalent to 1 billion seconds. This is just another unit conversion problem.
This showed up on the comics page just after this class one year. Gotta love it!
This allows us to think of 10 billion dollars as equivalent to someone throwing a $10 bill at us every second for this number of years. The US national debt is currently about 26 trillion dollars. That is equivalent to someone tossing $26,000 at you every second for this many years. It's still hard to grasp but its much more meaningful than just saying $26 trillion.
HW: Unit Conversion
How many years is 1 million minutes?
Assignment: HW Unit Conversion
Complete and assemble your solutions to all (2) the HW problems listed here showing all the steps in your unit conversions. Scan to a pdf and turn in on LMS. Please review HW format expectations for guidance about your homework solutions.
Reading Ahead:
Next you will read the chapter on Motivation from David's book before we start the next discussion. This chapter is one of the longer chapters in the book so don't get worried about the future. Take your time and realize you may need to read through it a couple of times to feel comfortable and be sure you understand the purpose of the text.
We will be working from the Graphs Breadcrumb along with this chapter.
