Winter 2005 Newsletter

Hi and happy World Year of Physics to you!!!  It’s a new year and a new century for “modern” physics. More details on the WYP later in the newsletter.  Hopefully you already have noticed and appreciated the new VIP logo. Thanks to Tony Wayne for his innovative design which replaces the “what-the-heck is-that?” logo I drew in AppleWorks about seven years ago. But the innovations don’t stop there. In fact to truly appreciate the logo you need to go to VIP’s web site at www.vast.org/vip where you can get the full effect. Tony has revised the entire site. If you haven’t visited lately, then you haven’t seen our web site! Check out the 18 different presentations that VIP provided at the December South-East Regional NSTA meeting. You can click on the links and down load the labs, demos and lessons that were presented.

!!World Year of Physics!! In honor of the centennial of Einstein's paper on special relativity and the 50th anniversary of his death, it's the World Year of Physics! If you'd like to check out all the possibilities go to http://www.physics2005.org/aboutwyp.html . Below I've pasted and described some sites that I thought looked the most promising for middle and high school students and would be easiest to jump right in and do.

• Poster Contest (ages 10-16) Deadline May 31, 2005 http://www.scienceacross.org/index.cfm?fuseaction=content.showcontent&node=374
• Physics Quest Learning Adventure! This one’s for Middle schoolers (teacher can register for class or individual students can pursue on own) http://www.physics2005.org/events/physicsquest/index.html
• US Physics Talent Search- students earn points for doing physics related activities, visiting physics related museums, university physics departments, conducting experiments and much more. Think merit badge for Physics!  (ages 10-19) http://www.physics2005.org/events/talentsearch/index.html
• Measure the Earth with Shadows  Join up w/ another school and repeat Eratosthenes’ experiment (physics, Earth science, geometry classes)  http://www.physics2005.org/events/eratosthenes/index.html

Spring Meeting Information

Who: You of course        What: Spring Meeting of VIP       When: April 23rd (time agenda below) 9:00 – 4:00

Where: the physics building, Jesse Beams Laboratory. There is a good web map at http://www.virginia.edu/webmap/.  Click on “G” The physics building is #41. You may want to park behind #38 off of stadium road.

Why: ‘Cause it’s a fun way to become better at what you do! 

What is the Luminosity of the Sun?

The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them.

Sir William Bragg (1862 - 1942)

Purpose: Apply the concept of the “inverse square nature of light” to determine the luminosity of the Sun.

• Do not look directly at the Sun or directly into a bright light source held close to the eye. Permanent damage to your vision will occur.
• The light bulb will get hot – do not touch.

Procedure:

• Plug in a 100 W light bulb in a sunny location. Hold one hand with its palm towards the Sun.  Hold the other hand with its palm towards the 100 W light bulb.
• Move the hand closer to or farther from the 100 W bulb until both palms feel “warmed” equally by the Sun and the 100 W light bulb.
• Have your lab partner carefully measure the distance from the palm of your hand to the center of the 100 W light bulb.

Useful Facts and Information

•The Sun is, on the average,  1.495987 x 1011 m away from the Earth.

•Luminosity is the total power output of an object in all wavelengths. The 100 W light bulb puts out 100 Joules of energy each second. Most of this is in the infrared (heat) with about 5%- 10% in the visible spectrum.

Analysis – Prepare and present to class

Determine the luminosity of the Sun.

Show mathematically how you determined the luminosity of the Sun. (white board)

Explain in a few well written sentences why you believe this solution is valid.

Describe in a few well written sentences how much faith you have in your answer? Provide an estimate of your percent uncertainty. (white board)

Teacher Notes

This lab is sooo simple! Leads to interesting discussions about “order of magnitude” measurements and uncertainty. The accepted value of the luminosity of the Sun is 3.827 x 10²⁶ W

Sub day plans?

The movie Fatman and Little Boy is a pretty good flick. It runs a full 2 hours and depicts the development of the first two atomic bombs.  As a movie it’s pretty good – I find my students watch it intently and almost none of them have ever seen it before. The assignment I provide them is to make a list of key people and events in the movie and, by gut instinct and prior knowledge, decide which are “historical” and which are “fictional”. After the movie is over we go through the lists and I lecture on the movie, the facts, and the discrepancies. http://white.stanford.edu/~brian/fun/fatMan.htmlis a site maintained by  Brian Wandell, a physicist who appeared in the movie who has his own take on how the producer handled the film. Do make sure you do a little research into the facts before you show the movie to make the discussion afterwards meaningful.

Einstein Received the Nobel Prize for what?

In 1905 Albert Einstein wrote three very important papers. The first concerned something that is today called the photoelectric effect. The second was what we now refer to as the special theory of relativity. And the third explained what is known as Brownian motion. The general population seems very aware of Einstein’s famous work having something to do with the speed of light and the odd things that occur when objects approach that Universal speed limit, but most mistakenly believe he received the Nobel Prize in Physics for his work on relativity. In fact, he received the Nobel Prize in Physics “for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect”.  The Photoelectric effect is a peculiar aspect of light and metals interacting first discovered by Max Plank.  It is a rather costly experiment to set up in high school. The equipment from a major vendor sellsfor $585.20. If this is out of your price range for a single set up, then the url http://lectureonline.cl.msu.edu/~mmp/kap28/PhotoEffect/photo.htm may be of interest to you. Of the photoelectric effect simulations I’ve seen, this seems the easiest to understand and the most attractive. It is set up to allow the student to experiment with the light intensity, wavelength, three different metals, and the retarding voltage.  It is my hope to demonstrate (and hopefully provide as a give away) equipment to demonstrate the concepts behind the photoelectric effect. (No, not the $585 version)

Look in your prep room. Do you have one of these? Get it out and learn to use it!                           It’s the commercial photoelectric effect equipment.

General Relativity? That’s A Warped Idea!

This one’s a bit messy. Get a coffee can – the big one. Drill several holes in the sides about 2.54 cm above the bottom of the can. Use an exacto knife to cut the plastic lid into a thin ring. Take some care to make the cut smooth. Whip up a batch of good soap bubble mix. [2/3 cup Joy dishwashing soap to 1 gallon water and add 2 to 3 tablespoons of glycerine (available at the pharmacy or chemical supply house.) this is the Exploratorium’s recipe] Place the “ring – lid” on the top of the can and invert it into some soap bubble solution. Place the can on a flat surface with the soap film stretched across the opening. The holes near the bottom allow air to move out of the can and the bubble to hang down into the can. Use a pipette to place a drop of cooking oil on the soap surface. Use the pipette to place a second drop on the surface. Vwalla! Attraction at a distance! If you release the second drop with the correct velocity you can achieve beautiful orbits! Equipment doesn’t get much cheaper. Students and adults will “investigate” (OK, play!) for many minutes. You have to try it to believe the conversations and questions that ensue. Great way to introduce gravitational fields.

Einstein – The 2 Minute Biography   

The experiment described below comes from the World Year of Physics’ Physics Talent Search. Students can complete and submit a wide variety of activities to earn a certificate that will recognize them as "United States WYP2005 Physics Talent,". If the student earns points equal to his/her age then he/she will receive an “International Honorable Mention”.

COEFFICIENT OF FRICTION

Goal: To determine the coefficient of friction between different types of sandpaper, and relate this to “grit size.”

Equipment and materials: a board (1-ft × 4-ft or larger, 5-ft in length or longer), a brick, 5 grades of sandpaper (1 sheet each), a tape measure or yardstick (you could also use a protractor.)

Procedure: There are two “kinds” of friction: static and kinetic. When a body rests against a surface and a force F attempts to slide the body along the surface, the resulting frictional force has the following properties. If the body does not move, then there is a static frictional force fs and the component of F parallel to the surface that are equal in magnitude and opposite in direction. fs has a maximum which can be determined by tilting the board and measuring the angle at which the brick “lets loose” and begins to slide. The static coefficient of friction, ms can then be obtained from the formula Fs,max = msNs where Ns is the magnitude of the normal force. Plot the correlation between ms and grit size (in microns if you can). e.g. take a look at http://www.woodzone.com/articles/sandpaper/ Is there a difference between different kinds of grit (glass paper, aluminum oxide, silicon carbide, garnet paper, ceramic)?

To explore further: Kinetic friction is harder to measure. As the brick (or other object) begins to slide, the frictional force rapidly decreases to a value fk. To determine fk you will need a different setup where you can give the object an initial velocity (which you can measure with a stopwatch) and then determine the time (or distance) it takes for the object to decelerate to zero velocity. If you measure kinetic (sliding) friction with sandpaper (so you can compare ms and mk for the same materials you will need larger sheets of sandpaper (to give the sliding object enough room to stop).You can also do fun experiments with a toy car on a track. Put oil, water or sand on the track and using a stopwatch see how these affect the speed of the car.