HELP ME BLOW THEIR MINDS (and then determine the forces involved)

August 13, 2011 10:58 PM

New physics teacher filter: What was the highschool physics lab or demo that made you fall in love with physics?

I'm working on building my physics curriculum for this year and I have a set of labs that came with the textbook my school ordered. Most of them are OKAY, nothing to write home about.

Everyone I've told I'm teaching physics seems to recall one lab that blew them away and made them really love the subject. One of my friends who has a PHD in physics even said that a cannon lab made him want to peruse physics as a career.

I was considering doing the bed of nails/sledgehammer/concrete block for my momentum and collisions unit as an example what I'm looking for, but any level of scope big or small is helpful.

So my question, which labs do you remember from high school or college as being epic and helped you really learn the material?

Bonus question: What demos should I do for the first day?

posted by JimmyJames to education (41 answers total)

Cover the physics of animation, sports, and the physics of superheroes. Artists, jocks, and nerds will love you.

Also, pretty much anything related to applied physics makes me happy. Students need to decontextualize physics concepts to get them, so thank you for asking this question.

Building a trebuchet/catapult out of PAPER was undoubtedly my favorite, though. All the other kids in my class used wood and my dinky little paper trebuchet was much more accurate when launching ping pong balls into a bucket.

DISCLAIMER: I never had the opportunity to take physics. What physics-related assignments I did, I did in calculus, art, and engineering class.
posted by These Birds of a Feather at 11:05 PM on August 13, 2011

(This was in a college class, so I don't know if you could adapt it). I recall seeing a professor release a large steel ball on a pendulum across the hall, then stand perfectly still when it swung back and narrowly missed his face. Of course, it had lost energy, so there was no way it was actually going to hit him, but it was pretty dramatic nonetheless.
posted by Gilbert at 11:20 PM on August 13, 2011 [4 favorites]

Two labs come to mind ... one, on ideal gasses, required that we go out to the parking lot and take a few different models of cars, move them so that the tires were parked on a sheet of graph paper, and trace the contact area. We used that plus the tire pressure to estimate the curb weight, and then did the same thing with as many people as we could cram into the car, the goal being to calculate the difference.

I thought it was a good lab for a couple of reasons, not least of which because it actually worked: the results were accurate to within 10% or so, if you did the tracing carefully enough, which was satisfying. (We had a fair number of labs conclude with the words: "Well, if it had worked, you would have gotten...") It also piqued the interest of a lot of students in the class who were not normally very engaged in class and generally thought it was uselessly abstract. (Possibly because it was an excuse to stand around in the parking lot unsupervised and partake in any number of vices, a fact that in retrospect there is no way our cheerful physics prof was unaware of.)

The other was an exam or heavily-weighted quiz at the end of the mechanics section. We walked out to an outdoor stairway that looked out on the football field. We were given some sort of spring-powered water balloon tosser, a long measuring tape, a protractor, and a spring scale (to pull back on the balloon launcher with). We each got a few ranging shots, and then the prof sat himself down in a chair out on the field. You got a grade based on how close you could get to hitting him, but the challenge was that he moved around periodically, so that you'd have to remeasure and recalculate the proper angle and tension to launch the balloon at, and you only had one or two actual shots that counted.

We did the usual highschool physics labs as well (Hooke's Law, alarm clock in a vacuum chamber, a fairly neat wave tank demonstration) and many of them were more pedagogically valuable. But those two were particularly memorable.
posted by Kadin2048 at 11:32 PM on August 13, 2011 [2 favorites]

i had a terrible physics teacher in HS...actually, a last-minute substitute who played re-runs of 'newton's apple' (the pbs series for elementary school students)...for me, what really grabbed me and turned me on to the subject (and led me to go back to school in physics and astronomy at CUNY, Richard Feynman's alma mater) was this image. i was looking for a picture of a mushroom cloud for an art project, when i came across it in a physics textbook on the sale rack at barnes and noble. i was staring at it for a minute, and then the numbers at the bottom just clicked and i was all like: "wait, what?"...might be a good opener to get across the sheer power of physics...
posted by sexyrobot at 11:46 PM on August 13, 2011

Not exactly what you were looking for but could be helpful if you want to do some inquiry labs. In my anatomy classes this year, I had students design running labs using Vernier force plates. A lot of kids came up with ideas that incorporated physics projects. The fact they designed the labs from start to end really captured their attention. One group investigated if there was a relationship between the force of their steps as they started running and their acceleration (they were baseball players examining stealing bases) while gym rats used resistence belts to manipulate the angle of their bodies while passing over the plates (vectors). Lots of folks looked for a relationship between their pace and force on the plate. We used a short selection from Born to Run to inspire ideas. I was very impressed with the experimental designs. Memail for more info if you'd like. Also, consider asking this same q to the #scichat community on twitter - they've always given me greats of advice. Good luck during your first year!
posted by adorap0621 at 11:55 PM on August 13, 2011

The prism in elementary school and the wave tank in high school.
posted by Lynsey at 12:16 AM on August 14, 2011

Most memorable for me was the Van de Graaff generator but I can't think of anything you could do in 1 lab that would make up for the rest of the 5 years - for some reason all the physics teachers at our school were either crap or really, really scary and grumpy. I don't think I know anyone that fell in love with the subject - even the ones that took is past 16 were only doing it as a means to an end. (required subject for the degrees they wanted to do)
posted by missmagenta at 12:21 AM on August 14, 2011

This wasn't until college, but learning that all the calculus I knew actually really beautifully applied to physics. I wished someone had taken me through that in High School, when I was just starting to learn the subject--I would have understood so much more of physics much faster.

@sexyrobot: When did Feynman attend CUNY? I know his bachelors is from MIT and his grad work was at Princeton...
posted by chiefthe at 12:29 AM on August 14, 2011 [1 favorite]

High school - getting people to hold hands, to make a circuit with a power source and a flourescent strip light, so it lights up. Conducting electricity through yourself is cool.

And another vote for the Van de Graaff generator.
posted by Coobeastie at 12:51 AM on August 14, 2011

When I taught conceptual physics for 9th and 10th graders, my students loved:
-balloon rockets
-checking the energy used in the school and measuring voltage in different rooms/appliances
-building roller coasters (less of a demo, more of a long-term project)
-pretty much everything from the NEED curriculum (it's a program run by PG&E that gives you a crapload of free lab projects - if you haven't been to the training, it's totally worth it...especially if Vanderwerf is still leading it in Oakland)
-comparing running velocity of each person in class
-making flashlights/simple circuits
-playing with goozac (or whatever you call the mixture of cornstarch and water)
-playing "Will it Float?" (seems elementary, but my kids loved it)
-keep the egg from breaking when dropped contest

That's all I can think of right now. But most of those things require limited equipment to run. And for my kids, being outside+science always equalled awesome. :-) It's more chemistry than physics, but I still remember my Advanced Chem class getting to make molten iron. Three years of high school chemistry and that's the only clear memory I have to show for it.

I also love the nail bed demo idea - it's an attention getter. And the Berkeley course Physics for Future Presidents is filmed and vodcasted for free - a lot of the experiments he runs in those are pretty awesome.

If I could make one more recommendation that's more method than content, I would say to do a really, really quick explanation of the concept you're demonstrating before the demo. You want them to be thinking about the MEANING of the experiment, not just the awesomeness quotient. Not to downplay the wow factor, but they're much more likely to remember the concept behind it if they know what to watch for. Another way of thinking about it is context - you're much more likely to remember a specific part from a movie if you see the whole thing rather than just seeing an isolated scene. Kids need context to know HOW to watch a demo. And afterward, connect it to as many examples as you can to further reinforce their knowledge and make the concept push into long-term memory.

As to the first day part, I started the year with states of matter, so goozac makes sense to me - it's fun (even if they've seen it before), interactive, and demonstrates a couple important concepts. But mostly it's fun and memorable. I also had (don't tell anyone) some liquid mercury that we poured out and watched the weirdness ensue.
posted by guster4lovers at 1:33 AM on August 14, 2011 [1 favorite]

Set up the double slit light experiment. Get them to predict what will appear on the wall you're projecting to. Blow their minds with the weirdness of what actually happens.
posted by fearnothing at 1:53 AM on August 14, 2011 [1 favorite]

I hated physics. But I do remember two cool projects. Building an electric motor and building a speaker.
posted by MuffinMan at 2:23 AM on August 14, 2011

I recall seeing a professor release a large steel ball on a pendulum across the hall, then stand perfectly still when it swung back and narrowly missed his face. Of course, it had lost energy, so there was no way it was actually going to hit him, but it was pretty dramatic nonetheless.
posted by Gilbert at 7:20 AM on August 14

Walter Lewin?

Some ideas in that video.
posted by Decani at 2:50 AM on August 14, 2011 [1 favorite]

Can't think of anything offhand, but I'd have to think there were some cool experiments from the old Mr Wizard show that should be recreated. I'd lament that your kids weren't even alive during his show in the '80s, but then again, I wasn't close to alive during his show in the '50s.

And there's also its modern incarnation, MythBusters.

It's really back-to-school time here on Metafilter, isn't it?
posted by TheSecretDecoderRing at 3:44 AM on August 14, 2011

Physics Demonstrations by Sprott.
posted by alby at 4:13 AM on August 14, 2011

I had a very practical physics teacher whose labs directly reflected the theoretical math. They weren't particularly interesting, but his problem sets and thought problems were.

At the end of tests, he'd put a thought problem for you to do if you have time. They were intentionally vague and usually covered material from the subsequent and not current unit. Two that stand out - "You're on a frictionless plane, naked. How do you move?" "Why do long freight trains back up before starting forward?"

The first question, I was very proud to have been able to get full credit for the single word answer 'excrete', since his was notoriously brutal to smart asses.

In college, I retook an equivalent physics class, mostly for fun and the labs were awesome. The were a little baroque and almost Rube Goldbergian in design, but they did what they did well. I'll describe two, first in goal, quick overview of the lab and then a detailed description of how/why they work.

1. Measure acceleration due to gravity. Drop a mass that marks a piece of paper at regular intervals during its fall. How it works: There is a steel/iron metal pipe that is set up vertically and is well-connected to house current. Taped to the pipe is a piece of very thin paper. Adjacent to the top of the pipe is a steel plumb bob that is held to an electromagnet. There is a flange that puts the bob within 1/16" of the pipe. If I recall, there was a loose wire that went from the steel bob to ground. When you cut power to the magnet, the bob falls. At the frequency of house current, power arcs from the pipe through the paper to the bob, burning a small hole through the paper. Using a frequency counter, you measure the frequency of the house current and the distance between holes in the paper. Using that and a little linear regression, you can get acceleration due to gravity. Do that in today's school climate? Unlikely, although if you did a decent spread sheet would let the kids do several runs practically.

At this point, it's probably cheaper to get a set of data recorders and send them up in Estes rockets and see if the force guides on the engines are right (or give student groups "unknown" engines and see if they can determine the class from measurements).

2. Predict ballistics. A plumb bob is hung from a string a known height from the ground. It is pulled up an additional distance and released such that it will detach from the string at the starting point. By converting potential energy to kinetic energy and solving for time in the air, predict where it will hit. This was a pain to get set up, but so worth it. The plumb bob was lead with two screw eyes in it. The bob was hung from the ceiling from a string. The string was NOT tied to the screw eye. Instead, the string was tied to a small metal U-clip with holes in the faces. The u-clip went over the screw eye and a pin was put through the holes in the u-clip, holding the plumb bob. A second string was tied to the pin and made just taught. Measure the distance from bob to ground. Tie a string to the second screw eye (which should be halfway down the bob and allows tying a third string to the screw eye that will be parallel to the second string. Pull the third string so the bob is raised from the ground a small height and tie it off. Measure the height of the bob. If you know the mass of the bob, and the distance between starting and resting points, you have mgδh (PE). From that you convert to KE and solve for v. Given the height from the ground you can solve to t_fall and using that and v, you can predict the point of impact. Have the students place a box of sand at that point. Burn through the third string. The plumb will swing up until the point where the pin through the top screw eye pulls out. At this point the bob is at its starting point and is in free fall. Hope they did the math right. The use of the pin makes a release system that introduces a tiny amount of frictional force compared to the mass of a large plumb bob. Burning the string is a swift release that introduces very little in the way of extra force to the plumb bob. The lab takes some time to set up, but once the measurements were take and the math done, the students should predict within a cm of the landing spot.

Didn't do these - but there pretty awesome.
If your school has a pool, show up there with all the students and a tumbling mat and a video camera (and maybe a step ladder). Set up the mat in the pool and get 4 students to hold the corners. Get a 5th student to climb on the mat at one end and stand up. Instruct the four students to let go and have the standing student walk from one end of the mat to the other in as straight a line as possible. Video from on high. Repeat but have the student walk in a circle on the mat. Observing students should be also taking notes. When you play back the video, you will see that the mat hardly moves. A nice demonstration of forces being applied equal and opposite.

Get a miniwan. Get three or four students with bathroom scales to stand behind the van. Have two students in the van, one with a pile of traffic cones and one with a stop watch. Van goes into neutral, no brakes. The students place the scales on the back of the minivan and push. When they are pushing at a constant force (signal to the kids in the van). At regular time intervals, the kid with the stopwatch signals the kid with the cone who drops a cone. After 10 cones or so. Stop the van and measure the distance between cones and record the force on each scale.

Using distance between cones, you can get the acceleration. Using that you can get the students to calculate the mass of the van (plus the mass of the students in the van and the driver - which you can measure using the bathroom scales...).
posted by plinth at 4:40 AM on August 14, 2011

I went to a lot of science demos (at engineering open houses, et cetera) when I was a kid, especially between the ages of 9 and 13ish. The bowling ball/pendulum nearly missing your face is a good one, and anything involving liquid nitrogen is really cool (literally, I guess), although also potentially less directly applicable to physics.

From my high school physics class, I remember a few classes in a row where we spent the whole time using these little pulley construction kits to complete different assignments the teacher had given us. It was really frustrating sometimes, but it was also fun solving the puzzles and trying to apply what we had learned in class.
posted by naturalog at 4:46 AM on August 14, 2011

slingshot water balloon- the big three person one- the ones that are made like of medical rubber stuff. The ones where two people hold the handles and one person pulls back the pouch. One kid measures the angle, and then we had to find where the balloon hit and measure the distance. (on the school field)

If you'd done anything like it before, you know that 45* gives you the best distance.
But still, GIANT WATER BALLOON LAUNCHER!
Then we launched balloons off a balcony over looking the sports field, and looked at height and distance.

Another thought- yes you want to blow their minds on the first day, but remember that you can also continue to do fun experiments and BLOW THEIR MINDS all through the year.

My teacher didn't really do this, but my sister's teacher did. I know which teacher was 'cooler'.
posted by titanium_geek at 5:36 AM on August 14, 2011

My favorite lab was one of the first weeks of high school physics. All we knew at that point were the kinematic equations. There was a contraption set up, with some sort of ball or weight hanging between two strings. You burned one of the strings, so the ball went into a pendulum motion. At the exact bottom, the string hit a razorblade and then the ball went into freefall. We were allowed to measure only one thing and then had to place a cup on the ground exactly where the ball would land.

Figuring out how to put all the equations together was like a big puzzle, and then coming to the realization that you only had to measure the height of the contraption and that it would work for any weight and any gravitational system was pretty cool.

However, I was a bit of a nerd to begin with, so YMMV.
posted by JannaK at 6:49 AM on August 14, 2011 [4 favorites]

Angular momentum conservation standing on a big spinning wheel. You know the one.

Running through the Noether derivation of conservation of linear momentum is simple enough (it's on wikipedia). Angular momentum is harder, but the illustration that you can use apparent physical laws and mathematical thinking to get at interesting behavior is kind of stunning.
posted by a robot made out of meat at 6:50 AM on August 14, 2011 [1 favorite]

For me it wasn't school, it was a book - The Flying Circus of Physics by Jearl Walker. There are plenty of stimulation, classroom-safe demos among the 600-odd topics. Off the top of my head: standing wave patterns, the drinking bird, siphon pumps, silly putty etc. I'm sure there are better examples but I don't have my copy on hand...
posted by fix at 7:10 AM on August 14, 2011 [2 favorites]

Ok, here's one that's pretty unique, required no "lab" equipment, and had us all wound up for a week.

In the '90s, a stunt motorcyclist died trying to jump a pedestrian overpass in Reno, NV (I think). Of course, footage is online now (liveleak) and easier to find than a newspaper article. If I recall the story correctly, it was a dumb publicity gimmick; maybe the whole point was to promote the grand opening of the overpass, or a tire store, or maybe it was just July 4th. I do remember that witnesses said the motorcyclist wanted to abort the jump that morning because of the high winds (check out the flag visible in the footage), but his promoter coaxed him into doing the jump. Intrigue!

Our high school physics teacher had videotaped all the news broadcasts and replays of the accident. We had footage from all angles, including a continuous shot from a helicopter. He also had the exact height of the overpass, and the ramp width. What he didn't know (or give us) was the driver's final speed, exact ramp profile, the wind speed profile, the cross sectional area of the driver/motorcycle, or anything about stunt motorcycle jumps in general.

In principle, one can use distance scales present in the footage, a stopwatch, analytical reasoning and estimation to fill in the details. The class was divided up into several groups; half the groups were charged with "proving" that the wind was sufficiently strong to cause the driver to miss the ramp, the rest were to "prove" otherwise.

Call it mock scientific forensics, if you will. It was just a classic ballistics/kinematics problem, but someone's life was on the line. It seemed like the whole class was captivated by the exercise. We spent one class hour watching the footage and taking measurements, and another learning about the drag force due to wind resistance (not in the curriculum, not the usual case of constant acceleration, totally relevant in the real world), and posing on a mocked up "bike" to estimate cross-sectional areas, etc.

In the end, it came out really close! Neither case could really be made conclusively. Meanwhile, analytical, critical-thinking-type statements like the following were emitted from the mouths of mere high school students:

"Ok, but since the wind force scales like v^2, if the wind gusted to 50 mph instead of 40 mph it would surprisingly increase his miss by x inches."

"If he left the ramp at just a 2 degree angle away from center, that could explain up to 80% of the miss at the landing ramp."

"We only know the total weight of his person and bike to within 20%, which means that the displacement due to the wind is only known to ..."

Finally, some interesting subtext: This physics teacher had an earlier career at the nuclear test site in NV. Part of his job was to go to court and argue that the a given underground nuclear blast had clearly not been the cause for the plaintiff's well/shed/irrigation piping coincidentally collapsing 100 miles away on the same day.
posted by fatllama at 7:18 AM on August 14, 2011 [3 favorites]

From a theoretical physics professional friend: "it wasn't no much the labs that got me going, which is why i'm a theorist now. But when we learned about Electromagnetism in the context of Maxwell's Equation, and that it can produce visible light, that did it for me". Maybe a bit esoteric, but could do something for them.
posted by AutoPilot83 at 7:32 AM on August 14, 2011

Our physics teacher had a contraption made of two now-legless office chairs facing inward from the far ends of an 8-10 foot metal rod, with an axle in the middle and a 5-gallon bucket on top of the axle. I think there was also another small bucket attached next to each chair seat. A big pile of tennis balls went in each small bucket, 2 students went into the 2 chairs, and a few more people helped to get them spinning. Then the students had to try to throw tennis balls into the bucket in the center. You could probably do this more safely/cheaply if you have a merry-go-round at a nearby playground. Lots to learn about momentum and frames of reference and vectors and stuff, though I've clearly forgotten most of it.

Our physics class also had a day at the local amusement park every spring, towards the end of the school year. There was a big packet of physics problems to go with many of the rides, but you could pick maybe 3 or 4 of them that were most interesting to you and your partner and then just enjoy the rest of your day. I don't think we had to carry around much equipment, so the problems must have been more theoretically based on the rides instead of requiring any actual measurements.
posted by vytae at 9:15 AM on August 14, 2011 [1 favorite]

Finding out how much power a human body can produce. Simply get some people to run up a flight of stairs and time them doing it. From the known height of the stairs and their times you can easily wok out how much power they were putting out.

BTW, this recollection led me to go googling for the physics teacher concerned. Found him in Canada, teaching in the aviation faculty of a technical college. No doubt of it being him--found pictures. AskMe rocks.
posted by Logophiliac at 9:56 AM on August 14, 2011

When did Feynman attend CUNY? I know his bachelors is from MIT and his grad work was at Princeton...

huh. you're right. how'd i screw that up?...i'm def. mis-remembering something...maybe he just taught/lectured there for a while?...I DID take astronomy 101 from Dr Michio Kaku, FWIW ;)
...good school, City College...NYC funding + most students from the 5 boroughs taking 'general studies'= nicely overfunded science program...low-temp research down to .00...(?)0003 degrees above absolute zero, laser crystal lab (where they make up new crystals for new colors of laser), biophysics program...etc. some pretty cool cats did go there at one point or another...Robert Hofstadter, Jonas Salk, Arno Penzias...
posted by sexyrobot at 10:03 AM on August 14, 2011

I liked the stuff on waves - I remember doing some of these experiments.
posted by analog at 10:28 AM on August 14, 2011

Optics demos.

We played around with lasers, mirrors, polarized film, double slits
posted by bleary at 10:38 AM on August 14, 2011

oh...speaking of optics...handmade holograms?
posted by sexyrobot at 10:47 AM on August 14, 2011

One demo my high school physics teacher did that was pure evil had to do with electricity and path of least resistance. He had a hand-cranked generator that had exposed metal rails that went to an incandescent bulb. He had a student come up and crank the crank for all they were worth while he had his finger across the rails. Then he would switch positions sending the student behind him. While out of view, he loosened the bulb a turn so that there was no longer a circuit, while simultaneously gesturing "shhh" to the class. The student put their finger across the rails and he turned the generator maybe once and the student let out a yelp. Switch back, again student going behind while he tightened the bulb. The student, now bent on vengeance, is cranking with all their might to no avail. Switch again, yelp.

You'd be surprised how much vengeance interferes with rational thought.

When I taught 7th grade and 9th grade technology, I had the students make their own speakers. It's simple - make a coil from armature wire - about a meter of wire. I had them put some paper over a 2" diameter PVC pipe and wrap the coil over the paper, then hot glue the coil to hold it together. Slide the paper off the tube and pull the paper out to get the coil. Glue a good button magnet to the bottom of Solo plastic cup and glue the coil around it. Strip the two ends of armature by brushing it with sandpaper.

I tested using an amp torn from a set of PC speakers that a student drove a pen through. Since the amp was fine, it was perfect for driving the speakers. There are a whole bunch of thought problems wrt observation of what happens when you put another magnet on the existing one or a chunk of iron. The coil will inevitably heat up and if you work it hard enough, it will melt the hot glue. Why?
posted by plinth at 11:12 AM on August 14, 2011 [2 favorites]

Agreeing with people who've mentioned speakers.

Anything with optics, electricity, magnetism.

And I'm not certain how cool oscilloscopes would be for everyone, but I loved it when we used them in demos. On my own I played with running current through a coil (demo thing for a rheostat?) to see how much it would push away the beam on the display. That wasn't a real demo, but when you have the parts around, your students can play with them.
posted by bleary at 11:22 AM on August 14, 2011

Cloud chamber! This hardcore guy actually built one out of, like, cardboard (just for rogue cosmic rays; reading reveals he didn't have a sample), but our teacher borrowed one from a nearby college. Most of what you see are alpha particle trails, but if you keep looking, you can occasionally see a beta particle (trail).
posted by skbw at 1:43 PM on August 14, 2011

A tube with some sort of flammable gas and holes in the top; the prof played notes into the machine (with a synthesizer I think?) and lit the tube, and you could see the flaming sound waves change as the notes played. It was uber cool.
posted by Acer_saccharum at 2:16 PM on August 14, 2011

Oh, and I know you didn't ask this, but trust me...get Thinking Physics - I used it for warm-ups every day (I know your school is big on bell-to-bell instruction and will love you for it). Some of the questions were WAY too hard, but if I remember right, they're multiple choice so there's still a way for kids to guess without all the requisite knowledge. Plus, it's a way to review material that you've taught before (remember: 50-100 repetitions for the average learner to "get it") and it's also great as a lead-in to the instruction for the day.

Best investment I made. I'd also second the book mentioned upthread - Flying Circus of Physics. That was pretty cool too.
posted by guster4lovers at 2:19 PM on August 14, 2011

I always thought that the monkey gun was cool.
posted by Daddio at 2:55 PM on August 14, 2011

Acer_saccharum: "A tube with some sort of flammable gas and holes in the top; the prof played notes into the machine (with a synthesizer I think?) and lit the tube, and you could see the flaming sound waves change as the notes played. It was uber cool"

Oooo. That's called a Ruben's Tube. I never saw one in person. That would be a kick ass demo.
posted by bleary at 4:11 PM on August 14, 2011 [1 favorite]

The Millikin Oil Drop Experiment!

(Just kidding. Don't make your students do this ever. It should be outlawed under the Geneva Convention. I had to do it in HS, and at two different colleges. It was extraordinarily unpleasant all three times.)

A few days ago, I was thinking about an experiment we did to demonstrate projectile motion that involved launching a marble while photographing it with a camera on long exposure ('bulb' mode) while lit by a strobe light. Once you captured your image, you could overlay some a grid over it, and note that the horizontal spacing between the images of the marble remained constant, while the vertical spacing did not. I always thought that it was extremely elegant in its simplicity.

Oh, and the bowling ball on a string nearly missing your face is always a fun one.

Ruben's tube is also indeed hella cool to watch. You need to have a lot of gas pressure to make it work though. Still...it's FIRE.
posted by schmod at 9:10 PM on August 14, 2011

Everyone knows the experiment where you put a postcard on top of a glass full of water and then turn it around to demonstrate the air pressure, which can be a fun way to get a discussion about air pressure started if it's done in a tantalizing way. But there's another experiment that is, in my opinion, much more impressive:

Get a bucket of water, a loooong transparent hose and take the class to the bottom of a stairwell. Submerge the whole hose into the water until it is filled, then lift one end, closing the opening with your thumb or a stopper. Lift the end of the hose further and further up while walking up the stairs - the air pressure will be strong enough to hold the water inside the hose until you reach almost ten metres, then the students will be able to see at the top of the transparent hose that the water doesn't go up any further.
posted by amf at 9:42 AM on August 15, 2011

"A tube with some sort of flammable gas and holes in the top; the prof played notes into the machine (with a synthesizer I think?) and lit the tube, and you could see the flaming sound waves change as the notes played. It was uber cool"

Thirding this. It is very, very cool.

One lab I remember from high school physics was about total internal reflection. The teacher put a light bulb in a bucket of water and cornstarch on the surface of the water. The bulb makes a disk of light on the surface (which you can see due to the cornstarch), and the goal of the lab is to calculate the vertical position of the bulb without touching the water.

Disclaimer: I am a huge nerd. But I did major in physics, so this lab has worked on at least one impressionable proto-nerd.
posted by zeptoweasel at 3:11 PM on August 15, 2011

The two demonstrations I remember most vividly from high school physics were the states of matter and the doppler effect. For the first, our teacher stood at the front of the room and enacted the different states. Standing still for a solid, slowly moving waving arms for liquid, jittery for a gas, and completely crazy for plasma. The classes looked forward to it every year.

For the doppler demonstration, she sent the class's most hyperactive student out into the hallway, told him to go to the farthest end and then run towards and past the classroom door while yelling. (Presumably she warned her coworkers every year!)
posted by MsMolly at 10:11 AM on August 16, 2011

I just saw this very cool video from a science/art exhibit that shows salt on a metal plate vibrating at different frequencies. You can see different patterns as the frequency changes.

Salt vibrations.

I think this would be a very cool demo to show in a class.
posted by bleary at 8:04 AM on September 11, 2011