Posts in Category: phenomena
sound tubes
Different musical instruments work because they play the note you want to hear. This seems obvious, but it’s no small thing to make something play exactly the right note, and leave out all of the other noise. How do they do this?
Instruments are made from lots of different stuffs and geometries. Some things, like violins and guitars, use tight strings to create their notes. Tuning forks and the reeds of a harmonica use vibrations of solid materials with specific lengths. Other instruments, such as organs and clarinets, produce the notes in a tube of air. That’s the kind of instrument I’m playing with here, except my tube is a simple piece of pipe.
You might not have a tuning fork to create this phenomenon, but is there something else you could do to make a tube sing? What other instruments could you create? What do you think the sound waves in the tube look like?
upward liquids
A lot of people don’t believe me when I tell them this, but I truly don’t understand how water crawls up a paper towel or string or piece of cloth. How does it get the energy to do this when it’s just sitting there; and the towel is also seemingly passive in the whole affair?
I’m a physicist and I work with many like-minded scientists. When I ask them about this phenomenon, they realize that it’s not all that simple, but probably it has something to do with electric forces in the towel and interactions with the water. I’m sure that this is part of the answer. But even so, I’m happy to admit that I don’t really understand it.
So, I assign the problem to my students and ask them to start to investigate different features of liquid absorption. They think of much better investigations than I would, and when we share these we start to come up with more ideas. To get them started, I’ve created this timelapse video of water moving up a cloth:
I thought my idea to speed up the video and include a clock in the frame was clever. I’m proud of that old-school technique.
What do you notice? What wonders strike you? What investigations could this spur? This is just the beginning.
Here’s what the scene looked like the following morning:
And then, later that morning, I detached the cloth and set the loose end on the table. It was originally dry, but then this puddle started to form:
Epilogue
In my classes, I see lots of really great examples of how this phenomenon can be turned into a research project with lots of different variables. Researchers create all sorts of different investigation designs with interesting variables and creative methods. This time-lapse video that Micah created gives a good impression of one of the hundreds of ways the climbing fluids can be studied, and it’s fun to see the process overviewed in just a couple minutes:
static cat
I like to tell students that cats love to do physics. Seldom do I actually get a chance to show them, however.
Thank goodness I can make videos so that I don’t have to bring Gus to class with me. Here’s some work we were doing together to investigate how balloons and cats stick together.
equinox sunset
Yesterday in class we talked about what it means to be the day of the “equinox.” We related this to the “equator” and to “equal” amounts of sunlight and darkness in our day. But I also remembered that this meant something about where you could expect to see a sunrise or sunset. That made me want to go watch the sun going down that evening.
Where I live, the streets are lined up in a grid lining up north-south and east-west. We also live up on the side of mountains where we can get a good view of the setting sun. So I went out that evening for a walk as the sun was setting into the really smokey horizon, sinking behind some distant mountains.
I really like our east-west streets, especially at this time of year and its counterpart six months from now. (I also liked that no one was driving on this stretch of road while I was in the middle of it.) This helped me get my bearings as I watched the sun continue to sink lower and slightly to the right–exactly where the street points. And, on other days, before and after the equinox and closer to the solstice, I can use these streets to show me where the sunset drifts as the seasons ebb and flow. It’s fun to watch this change through the year, and even to take photos of the different locations of a sunset over time.
I also posted a cropped version of this photo here on Instagram, but I think I like this long, tall perspective better.
Addendum
A few years later, here’s a couple more examples of images taken on these east-west streets. These are taken a week apart from one another:
elevator physics
I like to send people into elevators with scales that they can stand on while traveling up and down. It’s a great exercise because they get to see some physics that they are actively a part of. At the same time, it becomes a nice conversation piece as different, surprised observers come in and out of the elevator we’ve turned into a laboratory.
I spent some time myself on the scale on an elevator, and I made a point of recording a round trip from the bottom floor to the top and back again.
I think it’s really important for you to know that this scale, like many, is a little sticky and is probably only trustworthy within a pound or so. That is, I think anything that between 158 to 162 pounds is really the same. Keep that in mind as you watch.
You can watch the video as many times as you’d like and look for connections between the motions of the elevator and the readings on the scale. What patterns do you see? What do you think the cause and effect relationships are? In other words, what makes the scale reading change; and what does not cause the scale to change from its normal reading?
This might inspire other experiments you can do on elevators. Does it matter if the person is bigger or smaller? If the elevator is faster or slower? What if you were on a roller coaster or other ride that might move you in more drastic ways? Can you model how the pushes and pulls on the rider would change?
Epilogue:
I made a new video, this one without captions but a smoother responding scale. I think it could be useful for another round of observations, or even as a place to start:
Epilogue again!
intro to hot chocolate
For your lab, you’ll be investigating what’s known as the “hot chocolate effect.” You don’t need to know anything about this effect and you certainly don’t need to try to look it up or read about it. (This usually just makes things worse.) Instead, take a look at my intro and then use this as a starting point for your own investigation:
Truly, I hope you always tap the bottom of your mug from now on when you stir hot chocolate.
(I created this other post for the general public about this effect, too. I think the effect worked better in this video.)
hummingbirds in slow motion
I don’t have much to say about this except I really enjoy watching hummingbirds. Even in slow motion they’re still really fast. I like the way that they turn their wings and use their tails to maneuver, but I’m especially fascinated with how still their heads are while everything else is moving:
bees in slow motion
I put a camera at the entrance to a bee hive and took slow motion video of these honeybees. Each time I watch the video I see something different and am fascinated by the way that bees fly and control their path. I also just like their behaviors as well as some interesting play with the light. Oh, and you should be prepared to observe how the slow motion also affects the sound.
There’s a good bee blooper at the very end, too.
And here’s another longer video I took later from above the hive:
What do you observe about the bees and their behaviors outside of the hive? What about the way they fly and maneuver? How do they take off and land? What do you imagine they’re all doing? What else do you notice? What do you wonder? How could you study this, either with the video here or in another way?
Epilogue
It’s probably worth noting that I can politely hang out right next to all of these bees. They’re very busy and don’t want to bother me as long as I don’t bother them. In fact, my son, Reed, is so good at calming a bee that he can coax it onto his finger — something he did once when Victoria (the bee) was inadvertently stuck in the house and being chased by Gus (Reed’s cat). Honeybees are not only easy to live with, they’re important to our way of life. You might take a look at some things you could do to help honeybees.
I also have a few other resources:
- This collection of slides I used for a presentation on honeybees.
- A photo album of some of my photos of bees I’ve worked with.
balancing acts
If you see me in front of an in-person class and I have a meter-stick, you’ll often witness me trying to balance it in various ways. The most impressive and kind of magical way to balance a ruler, stick, baseball bat, etc., is using this trick of sliding your fingers towards one another. They naturally meet up at the exact balance point, even when the object is lopsided. Take a look:
I also like this video because it shows me messing up and dropping stuff, and there’s a great cameo of our puppy, Nina. Oh, and the intro and outro features my favorite band.
What other objects can you balance? Can you create an investigation around finding the balance point of an object under different conditions? How would that point shift if I kept adding weights to one end or another, or to a different spot? What other strangely shaped objects would balance this way?
raisins in soda
For some people in my family, there’s no good use for a raisin. I happen to disagree. I love them mixed in with nuts and candies, and I also discovered that they make for a great science investigation. When someone set aside all of their raisins, I decided to take video of what happens when I put them in soda water:
When you watch this, you probably have some observations, ideas, and questions. What makes the raisins go up and down? Why are some stuck on the bottom? Why doesn’t my family like raisins? For me, the more closely I look, the more questions I have and the more different things I’d like to try out.
While you’re thinking about this, here’s another video of the same raisins. This one is up close, and most of this video is shown in slow motion so that you can look really closely at some things going on.
You might want to look at this a few times closely, but maybe this is just the first step. If someone in your family doesn’t like raisins and shares them with you, maybe you’ll put them in a favorite drink and see what happens. There could be other liquids and other objects that could do similar things.