Homework 5, due Mon May 2, 2011
		Physics 12: Spring 2011

1. The three Gorges Dam on the Yangste river will be the largest hydroelectric
plant in the world.
The height of the water will be 80.6 meters and the flow rate will be
about 30000 cubic meters of water per second.  Assume 90% efficiency in
the turbines. (water weighs 1000kg per cubic meter)
a. Calculate how much power it is predicted to produce. (CALCULATE IT YOURSELF;
DON'T LOOK IT UP ONLINE; SHOW YOUR WORK and GIVE ANSWER IN Watts)
b. How many 1 GW nuclear or coal fired power plants will this replace?
c. The cost is around 30 billion dollars, more than 1 million people had to
relocate, and it may lead to the "environmental collapse" of the Yangtze river
eco-system.  Look up Three Gorges Dam online and answer the question:
"In your opinion is the three Gorges hydroelectric system worth it"?
Please write your answer in the form of a letter for the editor, backing
up your opinion with facts and giving clear reasons for what you are saying.

2. Suppose you have an medium/small 1200 square ft. roof, and you cover it with
photovoltaics.
Use information from the lecture notes to figure out how many kilowatt hours
you can get per month.  Look at your electricity bill (or someone elses)
and see whether the amount you calculated is more or less than the amount used.
Could you get all your electricity needs met with PV on your roof?
[Hint:  convert area to square meters and multiply by factor in lecture to
get Watts.  Then use efficiency of PV to reduce this.  Then multiply this
available power by time to get energy in one month.]

3. Where does all Plutonium come from?

4a. Name the material and enrichment needed to power a nuclear power plant
4b. Name the material and enrichment needed to power a fission nuclear bomb.

5a. A 120 lb person who normally eats 1700 Calories a day, fasts for one week,
on only water.  They keep the same level of physical activity as normal.
How many pounds of fat will they lose?
5b. The same person continues to eat as normal, but runs 3 miles per day.
How many pounds of fat will they now lose?
[Use 1 pound of fat is 3500 Calories and running one mile takes 100 Calories]

6. Write a list of good and bad things about solar energy.

7. Name the 4 types of solar power and write a sentence or two explaining each.

8. What is OTEC and why or why not will it become a major renewable source
of energy in the future?

Ristinen and Kraushaar Chapter 5:  Questions and Problems: 4, 5, 7, 8, 12
Ristinen and Kraushaar Chapter 5:  Multiple Choice: 6, 15