Need good physics demo ideas.

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Stucky101
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Need good physics demo ideas.

I'm ITAing for a Physics class. As an ITA I need to teach the class on my own once or twice a quarter. So I was thinking, rather than doing a mundane lecture I should do some sort of demonstration/experiment. Problem is the teacher is already planning to do all the obvious demos. So I need some creative ideas. Right now we're doing a unit on waves, but we're going to cover all the basic physics this year (kinematics, electrostatic, magnetism, force, ect.) so all ideas are welcome. Preferably something that won't burn down, blow up, or destroy the school or classroom (I was thinking of doing a demo that involves fire and natural gas... probably not a good idea).
"The earth is the cradle of humankind, but one cannot live in the cradle forever."
~Konstantin Tsiolkovsky, 1895

mochafairy
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Re: Need good physics demo ideas.

these were some things my AP Phys teacher did for my class. I don't know if the prof will be doing these, but they helped me understand the concepts better.
• use a jump rope to show harmonics, wave length, frequency, and velocity (tie one end to something, and then swing the rope up and down. you can change the wave length to show how it affects everything else)
• use a slinky to show how sound moves (lie the slinky down on the table, stretched out a bit, and push it forward a few times for pulses)
• if you can get your hands on a string and a woodwind instrument, you can use these to show relationship between pitch, tension, harmonics, string thickness, tube length, etc.
• you could also show that part from donald duck in mathemagic land! (this is my favorite, mainly because I love that video to death. they have it on youtube, if you don't have the VHS and/or a VHS player(side note, it also has a section that's awesome for visualizing solids of revoution))
• polarized light: get two polarized lenses and play
• i'm going to assume that diffraction is also apart of this, so get a laser and play!
• oh! get some string/rubber bands and some tension gauges. tie the string/rubber bands to the tension gauges and make it so there are two that are the same length/thickness but one has twice the tension as the other and then another that's the same length and tension as the first one but twice/half the thickness
• this video
• do a demo on the acceleration of gravity by dropping tennis balls from a known distance
• hot wheels cars (the demos and experiments are endless! friction! inclines! declines! projectile motion (lets figure out how high up this car has to be to go off the ledge to land in the bucket 5m away!)
• if have a power supply and a VOM/DMM, or access to one, you can make resistors and capacitors out of paper and pencil.You can show that proportional paper resistors have the same resistance. the difference between them is how much power they can take (and then, if you're like my class, you'll start making them smoke)

umm...that's all I can think of at the moment
"YES. DO IT WITH CONFIDENCE" ~fortune cookie

dedalus
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Re: Need good physics demo ideas.

Liquid N2 is your friend. I'm serious... If you can get your hands on the stuff, it's fairly easy to handle, and you can have a helluva lot of fun with it. Kinetics = Liquid N2 cannon for sure. If you set the cannon up horizontal, and drop a ball from the same height at the same time (trigger mechanism is needed) then you can shoot the ball out of midair 100% of the time, which looks mad. Same for expansion of gases... and I'm sure you can find something similar for 'forces'.

There's various experiments I've seen using balls of different metals to show their different heat capacities/conductances, but I'm not really sure exactly what you'd consider 'standard experiments'. Likewise, with the diffraction grating + laser beam, or getting 2 notes slightly out of tune and showing the interference.
doogly wrote:Oh yea, obviously they wouldn't know Griffiths from Sakurai if I were throwing them at them.

Stucky101
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Re: Need good physics demo ideas.

Well thanks for the suggestions, some of those demos sound fun but they either don't fit the curriculum of the class or the teacher's already planning on doing them. We're moving into a unit on light and other EM waves pretty soon and I need to do a lesson within the next few weeks for a grade. So I think I might just do a simple diffraction and reflection demo.
"The earth is the cradle of humankind, but one cannot live in the cradle forever."

~Konstantin Tsiolkovsky, 1895

TaintedDeity
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Re: Need good physics demo ideas.

I did those subjects last term and the ones I enjoyed most were using a length of elastic, a vibratey thing and a stroboscope to show stationary waves, getting a laser out and doing some stuff with diffraction and reflection and using a water trough to show how waves act by using an offset motor to dip something in and out of the water.
Oh yeah, we used a stroboscope for that too. Seriously, if you can get a stroboscope involved, you really should

Wave experiments with microwaves were kind of dull because we couldn't see them and they didn't work too well so it might be nice to keep those to a minimum.
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dedalus
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Re: Need good physics demo ideas.

One of the cool ones with an IR LED is showing how this apparently broken light gives off a light when a picture is taken (cameras pick up the IR EMR).
doogly wrote:Oh yea, obviously they wouldn't know Griffiths from Sakurai if I were throwing them at them.

BlackSails
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Re: Need good physics demo ideas.

Giant bowling ball!

Tie a bowling ball to a hook on the ceiling. Then step back, pull it to your face, let it swing in pendulum motion back to your face (make sure not to move) to show how you trust in conservation of energy.

simdude
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Re: Need good physics demo ideas.

I'm pressed for time but the video speaks for itself. In Clifford Stoll's TED talk he describes how he measured the speed of sound using just an oscilloscope with 8th graders. He also mentions they also measured the speed of light. It starts around 11:00 if you want to skip the rest of the talk (but I could never recommend that since it's such a favorite of mine).

Edit: I LIED! I can't stop thinking about various experiments! Here is a link to a demonstration I first saw in the MIT open courseware in Walter Lewin's intro physics class, where a spray paint attached to a spring can paints a sine (or cosine...you picky people you) wave across a roll of paper to demonstrate the harmonic motion. http://www.youtube.com/watch?v=P-Umre5Np_0

And speaking of Walter Lewin (who I am also madly admire), he does amazing demonstrations in general. It's still harmonic motion, but I cannot possibly think of a more engaging demonstration than using yourself as a pendulum!!! I couldn't find an isolation of the demonstration, but it begins at about 46:30 http://www.youtube.com/watch?v=__2YND93ofE

Stucky101
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Re: Need good physics demo ideas.

Well I decided to do some further research on my own and I've managed to uncover a real gem of physics demonstrations, or at least I think its pretty cool. Given that the class I'm ITAing for has only been introduced to basic physics 4 weeks ago, I would really like a demonstration that can easily be understood in their terms. Meaning, I want a demo that someone who doesn't even take physics could understand; and I think I've found the perfect one.

Its a demonstration in which a class finds the speed of light using marshmallows. We're introducing the students to light waves next class so I'll probably do it then. Should be fun. Link to the demo is below.

http://physics.umd.edu/ripe/icpe/newsle ... rshmal.htm
"The earth is the cradle of humankind, but one cannot live in the cradle forever."

~Konstantin Tsiolkovsky, 1895

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Re: Need good physics demo ideas.

On the subject of light, the double-slit experiment is an absolute must. Sure, the underlying dynamics are a bit advanced, but that experiment is probably the single most elegant way to show the true (well, until a working TOE emerges, perhaps) nature of light and of wave interference.

Also, if you can get your hands on anything with which you can demonstrate negative refraction, then that would also be absolutely awesome.