Physics lab gets spooky on Halloween
November 6, 2015
On Halloween, which was Saturday, more specifically: Saturday, Oct. 31, 2015. Well, really specifically: Saturday, Oct. 31, 2015 from 5 p.m. to about 9 p.m. Anyway, where was I going with this? Oh, yeah, on Saturday, which was Halloween, the UW–River Falls Society of Physics Students and Chem Demons held their annual Haunted Lab.
Side note: “haunted” does not look like a word, it reminds me of the word “haunch.” That’s just weird.
Back on point, the Haunted Lab is a very not spooky event held on the second floor of Centennial Science Hall. There are a few demonstrations related to physics and chemistry offering a range of involvement for the masses of people passing through. I ended up helping with the hovercraft. Which is loud. Very loud (pardon the fragments, they just reinforce the point). The machine is a large circular piece of plywood with a leaf blower strapped to it. According to Physics Professor Earl Blodgett, those who built the machine had bought a powerful leaf blower with variable speeds, so as to experiment with the amount of force needed to lift people of various weights. As it turns out, the thing needs to be on its lowest setting at all times and can handle something like 500 pounds.
The leaf blower pumps air through a hole in the plywood and into a tarp taped to the bottom. This tarp then has a bunch of holes punched into it to let the air out in a fairly distributed manner. The result is the machine and its passenger (securely sitting on a chair that’s just sort of set atop the plywood without any straps or belts) floating ever so slightly above the ground. The floating is controlled by a button, holding it down makes it float, letting it go makes it drop. Many of the patrons of the event said this gave them a very satisfying mystical feeling. Magic (again, apologies for the fragments).
What made this display so fun was that it made the friction between the machine and the floor negligible, so the rider could just slide around with ease. Now, here’s the thing that bothered me. When you are pushing an object, there is normally friction. So, when you apply a force, it is partly counteracted by this friction. And therefore slows down quickly. Both momentum and friction are proportional to the mass, so the friction tends to balance out the momentum. In this demo we nearly remove the friction, leaving the momentum to do whatever it pleases. These people were all being pushed down the hallway at about the same velocity, meaning that the larger passengers (e.g. the adults) would have that much greater momentum… so they would slide… and slide… and slide… then collide with the people at the other end of the hall doing some other demonstration. This meant that I needed to make sure the machine slowed before reaching that point, in the case that the passenger did not realize this and subsequently let the hovercraft drop to the ground where it would have friction to act as a break. But whatever.
Enough about the massive floating machine of ear-torture, there were other fun little science-y show-offs as well. There were some tubes with indicators in them, so they changed colors. The pH would change because they had dry ice on the bottom, which would then sublimate into CO2 and partly dissolve or something. There were bubbles and colors, cool.
Next, there was the “flaming tube of death,” which, just as the name implies, is a tube that is flaming. It was a bit more complicated than that. Basically, the tube was filled with gas and had an array of holes on top out of which the gas would flow. This outlet of gas would be lit aflame and so the tube would have a fire-ridge. On either end of the tube was a speaker, which would play a sine wave. The wave would be visible in the flames as the sound pressure things happened and gas does squiggly science. It kind of sounded like R2-D2 dropping some sick beats, which was fine for the first 30 seconds and obnoxious thereafter.
Fire was a recurring theme: there was a pumpkin that spat out a sizeable flame, which I was only able to catch a glimpse of; and methane bubbles. Bubbles are cool, especially when filled with flammable gas and popped with a candle. The physics department’s infrared camera was there to show off how hot these bursts of flame were, and also the big splotch on the ceiling where the majority of them were lit. The ceiling tiles are fire-resistant… probably.
Then there was a spinning thing for angular momentum, an electromagnet to show off how induction works, the floating shark thing that floats about because it is filled with helium… and something else… that I can’t remember… so I’m making it sound suspenseful… oh, the x-ray machine, which had an apple with some nails or something in it and also a cellphone.
Tardigrades and blobfish were topics of discussion at the event, but honestly, probably completely irrelevant to the demonstrations as a whole.
Trevor Hoglund is a student at UW-River Falls.