Jumping Ring (Elihu Thomson Coil)

The plans to the right are from Brown University. Click to go there.

Jumping Ring video from MIT. Embedding disabled. More videos from Wake Forest.

.pdf plans from Sam Sampere are simplier to build.

Magnet Falling in a Copper Pipe

Not me in the video, by the way.

Eddy currents. The magnet falls far slower than you'd expect because it generates electricity in the pipe as it falls. That electricity then generates a magnetic field in opposition to the magnet's field slowing the fall. Coolmagnetman has a good site expaining what is happening and a couple of cool experiments to try with it.

Bill Beaty's (my hero!) has lots of cool stuff about rare earth magnets here including excellent plans and sources for pipe.

Vacuum Cannon

Lots of sites explain how to put them together. I like Sam Sampere's construction plan, but I use BYU's method of sealing the ends with Mylar.

This article from California State Chico does a great job of explaining the physics of the cannon.

More on figuring out the speed.

Singing Rod

The singing rod works via stick-slip forced vibration leading to resonance similar to a wine glass. However, the natural frequency of the rod is higher than the wine glass, so you need rosin to make your fingers more sticky rather than more slipprey like in a wine glass. This is rather more detailed than you will probably want.

One note, the first site at the Whelmers suggests that the singing rod is vibrating transversely. I'm pretty sure that's not the case. Put the end in water and you will see the water making concentric circles which looks quite a bit different than what a tuning fork looks like in water.

http://www.mcrel.org/whelmers/whelm10.asp
http://www.arborsci.com/detail.aspx?ID=491

Invisible Glass

Philosophical sounding question: How can you see somthing that is clear like water or glass? Reflections, yes, but more so, distortions of light coming through. The distortion is caused by light being bent when it changes index of refraction. This site will teach you how to mix up a solution with the same index of refraction as Pyrex. When submerged, the glass will be invisible.

http://gr5.org/index_of_refraction/babywess.jpg
http://www.exploratorium.edu/snacks/disappearing_glass_rods/index.html

Bed of Nails

Lots of good sources here. Start with this Australian site http://www.keypoint.com.au/~skeptics/Bed_of_Nails which does a good job of explaining how to make a bed, although I'd recommend going with galvanized or stainless steel nails even though they are harder to insert. Rust is a bad thing here.

This U. Pitt site gives a pretty good take as well. http://www.pitt.edu/~dwilley/Show/NailBed2.html.

If you have access to The Physics Teacher, there's a great article published in October 2004.

Another method with a video.

Bed of Broken Glass

The bed is 70 pounds of broken glass, mostly window panes. Yes, I walk on it barefoot. No, I haven't cut my feet yet. No, I don't have students do it.

I followed David Wiley's advice pretty much exactly. http://www.csicop.org/si/9911/willey.html

Who knew that everytime I was doing this activity I was deriving some valuable reflexology benefits? http://www.lifeevents.org/walking-barefoot-on-broken-glass.htm