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Todd Marshall

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Energize!

January 20, 2004

Welcome to the College Physics website on Planet Psi. I hope you will visit here often.

Onsite you will find several classroom and study resources: a copy of the syllabus handed out the first day, problem assignments, lab info, and features I haven't even thought of yet. Be sure to look at your Class Resources page for study tips and other valuable information. I plan to add at least one new entry each week that will summarize and clarify the material covered in class.

What Is Physics

So what do we cover in class? What is physics?

I like to think of physics as a study of different kinds of energy: mechanical, thermal, wave, sound, electromagnetic, light, atomic, and nuclear. (What would you think if we renamed the class Energy and You?)

Tools of the Trade

To begin with, we will become familiar with measuring, measuring devices, and standard units of measurement.

We will also briefly review algebra and trigonometry. Remember, college algebra and high school trig (or their equivalents) are prerequisites for this course. Your algebra skills will be critical to success in College Physics.

You will need a calculator, but the fancy graphing calculator is not necessary. If you have one, that is fine, and by all means use it, but all you need is any scientific calculator with trig functions. (If you have to buy one, they are available for $10-$20.)

Motion, Energy, Momentum, Conservation, Rotation, Fluids

Our second major area will be the study of objects in motion, followed by the study of how they get into motion in the first place — and how to change that motion. We will define mechanical energy and momentum, and learn about conservation principles. Finally, our study of classical mechanics will deal with rotation and fluids.

Thermodynamics

Our next major area will be thermal energy and how heat can be used to do useful work. By this time we will have arrived at the end of the semester.

The concepts and principles we discuss will also be put into their historical context. We will learn about the major players in the physics world and their contributions. It's important to note that the physics we will learn this semester was basically figured out before the beginning of the Twentieth Century and as such is deemed "classical" as opposed to "modern."

Building Knowledge,
Concept by Concept

Physics is a discipline of logical progression and interconnected concepts. It is important to realize from the beginning that each concept we study is important to your understanding of the next concept. No chapter in your textbook is completely independent of the material that precedes it.

However, don't get discouraged if you don't get everything right off the bat. Physics concepts build upon each other, so you will see the concepts appear time and again. You will have the opportunity to review on-the-fly and reinforce material previously presented.

One warning: we will be moving at a fairly good pace. At times we may move ahead before you think that you are ready. Don't get discouraged. Keep up with the reading and the homework. Ask questions in class and visit Planet Psi and the companion website for your textbook. Take advantage of my office hours. I may also be available even if it's not an official office hour. If you can't come by in person, I may be able to answer your questions on the phone or via E-mail.

I hope this little web chat has given you some idea of what we will be doing this semester. For additional study hints see the Class Resource page and be sure to check out the Physics Lab page, too.

??

Week Two

Psi
Quest


Answer to Week Two Psi Quest

I gave you a speed, and you need to find a time. (The exact question is printed below.) Since speed is distance/time, you also need a specific distance not given in the problem. For the simplest solution and the smallest amount of time, you need to find the length of a tennis court. Hence your quest.

According to Accurate Tennis Construction, Inc., a tennis court is 78 feet long from baseline to baseline.

Since I have speed in miles per hour and distance in feet, I converted the speed to feet per second.

(140 mi/h)(1.467 ft/s)/(1 mi/h) = 205.4 ft/s

Then I solved the basic relation for t and calculated the answer.

x = vt
t = x/v = (78 ft.)/(205.4 ft/s) = 0.38 s

The opponent has at least this amount of time since the ball has to bounce first and that may slow it down a little. One of your fellow students also went so far as to find out that it takes a server 0.3 s to hit the ball, so the opponent has this extra amount of time to try and anticipate where the ball will go.

The serve was an ace, and I don't think Andy's opponent even saw it.

(I made a rough calculation taking the bounce into account, and got the much longer time of 0.41 seconds!)

THE QUESTION:Tennis star Andy Roddick hit a 140 m.p.h serve at the U.S. Open. How much time did his opponent have to react? Explain how you arrived at your answer. Be sure and give any references that you might have used. The deadline was September 5 at 5 p.m.



Answer to Week One Psi Quest

John Harrison solved the longitude problem by inventing a clock so accurate that sailors could determine their longitude to within half a degree. Measuring longitude depends on knowing local time in two places. The difference in these times multiplied by 15 degrees determines how far apart the two places are. Local noon at sea can be found by marking the time when the sun is at its highest point in the sky. By using a clock set at the local time of their home port, sailors could calculate the longitude of their position relative to this port. The clock that kept home port time must not gain or lose time due to weather conditions (temperature and humidity) and the motion of the ship. Harrison's clocks compensated for these conditions and kept extremely accurate time.

Longitude by Dava Sobel provides a fascinating look at John Harrison's life.

All of you who sent in an answer got it right. Congratulations!

THE QUESTION: Who was John Harrison? What great scientific problem did he solve and what was his solution? (Hint: Eighteenth Century.)


Dr. Heather
Woolverton
Autumn, 2003

WHAT DIS?

Dark Universe

BBC reports that the future looks darker and darker: Astronomers have confirmed by a new method one of the saddest stories of the Universe — one day the stars in the sky will all stop twinkling.

Ozone Satellite

A satellite designed to monitor the depletion of the ozone layer — with an emphasis on changes occurring over Canada and the Arctic — was launched on August 12.

Fate of the Hubble

The New York Times enthusiastically endorses the Hubble Space Telescope, but at what cost? Read the editorial about the future of U.S. space exploration.

New Life Form

NASA scientists have discovered a new extreme-loving microorganism in California's exotic Mono Lake. Astrobiologist Richard Hoover likens it to life on Mars.