One of the more useful skills that you can gain is to become adept and order of magnitude estimation (you will amaze your friends and maybe even win money from them ...:) )

Today we will try a bunch of practice problems to hone our skills.

The basic rule set for doing an estimation problem is

• Understand the problem and what is being asked

• choose a set of consistent units

• try to scale up a local example that your familiar with or define a standard "thing" to scale

• devise an estimation plan

• turn the crank on your plan

• perform a reality check on your result this important step is often completely forgotten

To begin with, I will work these two problems as an example:

• How many McDonald's restauraunts are there in the USA

• How many grains of sand are on all of the world's beaches?

Some practice Estimation questions:

The goal of this exercise is to compare answers and methodologies for arriving at these various estimates. Answer each question first in the worksheet and then publish the answer to that question. When all results are in, we will move to the next question.

Fill in your estimates in this worksheet Note - only input numbers, no text characters.

1. How many gallons of gas (in units of millions of gallons) are used in US automobiles on a daily basis?





2. How many megawatts per year could be saved if every American Household had only CFLs in them? (Assume we replace each 100 Watt Incand bulb with a 20 Watt CFL).





3. Estimate the total number of sheets of 8.5 x 11 inch paper used by all the students at the University of Oregon in an academic year. Now assume these sheets are stacked on top of each other at a thickness rate of 500 sheets per inch. How many equivalent 100 foot high Douglas Fir trees does this represent.





4. Estimate the total amount of power (in Kilowatts) that could be generated in the summer if every UO Parking lot were covered with solar PV arrays. Assume 10% efficiency for PV panels and incoming solar radiation of 1000 watts per square meter.





5. Microhydro on PLC. Suppose that the roof of PLC



were engineered so as to collect all the rain fall on it and drop it down to a turbine. If 10 centimeters of winter time rain could be collected and dropped down to a generator at the base of PLC, how much energy could be generated? The density of water is 1 gm/cm³ and 1000 kg of water dropped from a height of 10 meters = 25 watt hours.