Wilberforce Pendulum questions

Why did the Wilberforce pendulum swing?

I beg your pardon, but my pendulum doesn't swing! (See the real answer below.)

5.) Why does the pendulum stop, turn, and then bounce up and down?

If you have a slinky handy, try this: hold the two ends of the slinky, one in each hand. Leave five or six coils between your fingers and pull the slinky slightly open. Can you feel it twisting? The coils of a slinky, as they bounce in and out do two things. One is they bounce, the other is they twist. When they are bouncing, they are producing a strong twisting force, and when they twist they produce a bouncing force. The result is that they go back and forth between just bouncing and just twisting.

I am really glad you didn't ask me how the slinky remembers what it was doing last when it is exactly in between bouncing and twisting. I don't know the answer to that. Maybe it has to do with the way the slinky spirals and the direction the weight is turning. I'll have to watch more carefully next time!

6.) What is the pendulum used for?

The Wilberforce Pendulum is useful for teaching students about physics and not much else. On the other hand, a scientist here at the lab told me that NASA once launched a satellite that had springy antennas (so they could fold up for launch) and when it got into orbit it acted in a very confusing way, and wouldn't stay aimed straight. They figured out that the antennas were bouncing around like the Wilberforce pendulum and upsetting the satellite.

Please explain how you do the rock and string demonstration of weight and mass.

Our rock on a string is a fancy version of something you can easily do yourself. We do it dozens of times a day for weeks at a time, and so have come up with that system. You can do it more simply.

This demonstration comes from a book you might find in the public library called TURNING THE WORLD INSIDE OUT.  First you need a fist-sized rock. It will be easiest if it is a little rough so you can tie your strings to it. Then you need some string that is weak enough that the rock almost but not quite breaks it. We use crochet thread, which you can get at a craft store, but sewing thread will work too. Make sure you can easily break the thread without hurting your hand. If there is any chance of hurting your hand, borrow a leather work glove and wear it. Also please make sure the rock falls on something soft and keep us both out of trouble.

Tie two loops (slip knots) in two pieces of string and slip them around the rock so one holds the rock up and the other pulls it down. Now if you pull the bottom one quickly, it should break, if you pull slowly the top one breaks. To be really honest, if the strings are breaking where they are against the rock, instead of on the tail you are pulling, you should tie a stronger piece of string around the rock tightly (duct tape is good.) and tie your weak strings to that.

String breaks when it stretches too far. Because of its inertia (mass), it is easier to move a massive object that is standing still, such as your rock, slowly than it is to move it quickly. When you pull slowly, the rock moves slowly, and your pull and the force of gravity (weight) add together, putting more stretch on the top string. When you pull quickly, the inertia of the rock makes it stay still, and the bottom string snaps before the top one.

I need to warn you that sometimes this experiment misbehaves and the "wrong" string breaks. Actually the right string always breaks, just not always the one you wanted or expected. I once even had both strings break at the same time. But that's physics for you!

I hope you enjoy this project, let me know if you need more information. Good luck!

Please share a list of Circuit Connection Program Materials.

First circuit: The switch, lamp socket, and six-volt lantern battery are all conventional hardware. The bulb is a special 50 watt 12 volt light bulb intended for use in RVs boats, or houses that use solar or wind electricity off the grid. Ask about it at a hardware store.

Block-o-trons: The model electrons we pass around a circle. We made these blocks on a table saw, but any similar objects would serve the purpose.

Snap Circuits: This kit, by Elenco, is available in some stores in Santa Fe and can be found on the Internet, try http://amazon.com or http://thetoyhunt.com. The Toy Hunt website has a plethora of add-on kits. For the very best price one should Google “Snap circuits.”

Balloon Fuses: We use high quality balloons. Thinner balloons will pop easily on contact with the steel wool. The steel wool is the coarsest grade we found in a hardware store. Be careful, it has sharp edges, and it is easy to cut one's fingers pulling it out of the bag. Cut it with snips or scissors. The aluminum foil wires are simple strips of aluminum foil rolled and flattened into wires. Masking tape binds the ends of the strips over the ends of the steel wool to the balloons. Connecting batteries will heat the wire sufficiently to pop the balloon if the steel wool is about half a centimeter or less long between the ends of the foil strips. Two “D” cells works faster than one, but one will do the trick, too.

Conductor or insulator?: The electronic parts of this are mostly available from Radio Shack. We use battery holders, alligator clip leads, light bulbs and light bulb holders. A more complete source is http://allelectronics.com on the Internet, or Google the items you are looking for. Science supply companies, like NASCO, have these items as well. The sample conductors and insulators can be a collection of any sort of thing from around the house or around school. Nails, aluminum foil, plastic items, wooden things, marbles, jewelry, etc. all are interesting to test.

Where do we get information for our scientific explanations at the Bradbury Science Museum?

A lot of our information, especially about our exhibits, comes from scientists working in the fields of those exhibits. At Los Alamos National Laboratory, we have lots of scientists working on many different kinds of projects. Some of the information comes from research we do on a particular subject. We have people who take that information and try to make it understandable for our typical visitors. We also have a very talented exhibit designer, and a terrific exhibit builder to make the displays attractive.

The educators teach lessons that we have researched, and some of the information comes from classes we had in our elementary, middle, and high schools, as well as college. We all went to college. We have also had many interesting conversations with scientists. We read science publications, journals, and magazines, as well as articles in the newspaper. We do a lot of research in books and on the Internet.

Speaking for myself, I love reading books. My favorite books are non-fiction, books about things that are real. I am never very far from a book, and right now I am reading three at the same time! (I don't recommend reading more than one at a time, but this is just the way I am.) Many of the facts that I like to share come from books I have read, many of them long before I had any idea that some day I would be using that information to teach to students.