rallain | August 21, 2010Let's play a game. I think this will be fun. So, a couple of years ago I had the duty of organizing the physics demo room (well, "demo" is maybe not the best term). This room is quite large and there is a whole bunch of stuff in here, some of the items are very old.
There were lots of items that I knew exactly what they were. But, there were other items that made me go 'huh?'. So, here I will post an item. You post a comment regarding what you think it is and what it is used for. Some of these items I know the answer to, some I do not. Some of these pictures might just be part of a…
rallain | August 20, 2010I am not normally a book-review-kind-of-guy. However, in this post I will make an exception. My wife (who clearly knows me very well) bought me this book - Made by Hand: Searching for Meaning in a Throwaway World (amazon link)
The basic idea of the book is to look at how the author (Mark Frauenfelder) started doing more and more Do-it-yourself type stuff (DIY). He goes through his efforts to grow his own stuff, raise chickens, build guitars and stuff like that. Very enjoyable read. It wasn't so much about how to do stuff as much as it was about making stuff rather than buying stuff. (do…
rallain | August 20, 2010Reader Jorge has also looked at these amazing basketball shots. (here is my last basketball analysis) Jorge claims that at least one shot seems fake. He is referring to the following video (at around the 2:20 mark).
ARRGH Ok, new plan. For some dumb reason, youtube won't let me embed this video. Well, here is a link - Amazing Basketball Shots: The Legendary Shots 4 (at least I can link to the right time). It is even dumber that you can't embed it, but youtube gives you the download option. Oh well.
Let me tell you the part that Jorge has an issue with. This guy on a ladder throws a…
rallain | August 19, 2010First, where does Chad come up with these links? Oh, I am talking about Chad from Uncertain Principles. In his latest links of the day, I found this:
Skip Class Calculator
What a great idea. Basically, you enter some info about the class - like how often it meets, how many classes you have skipped, when is the next test and stuff. The calculator then tells you if you should go to class or not. Brilliant. Actually, this seems like the academic version of Run Pee. Yes, I said run pee. Run Pee is an app for your iphone that tells you at what point during a movie you can go to the…
rallain | August 17, 2010Let me start with the video. Here is a guy flying a plane in a barrel roll and pouring some tea at the same time. Talk about multitasking.
How can he pour upside down? Well, there are two ways to look at this. First, I can look at this in the frame of the plane. For this case, I can invoke the fake force - centrifugal force. Oh yes, I am going to do it. You probably remember all your physics instructors warning you to never ever do this. Well, they say that because they are afraid you will do something bad with it. Here, I will only use the centrifugal force for good.
What is the…
rallain | August 17, 2010I see that Doug at Nanoscale Views has fond memories of the hit show The Mechanical Universe. If you have never seen this show, it is quite excellent (even if old).
Perhaps the best thing about The Mechanical Universe is that it might be the best that traditional lecturing can provide. Oh, I know it isn't quite the same. Students can't ask questions while watching a video. But the main point is that if you want to go with some type of traditional lecture style format for a class, you would be hard pressed to do better than this. Or maybe something similar - there are other good video…
rallain | August 16, 2010I can't let it go. There is more here to explore. First, I can't believe that I looked at braking and then turning but not turning then braking. And what about braking while turning? I will model braking and then turning - but it won't stop here.
Consider a few motions. I could turn and then brake (which I am looking in this post). Another option would be to brake and then turn. I already showed that this takes a longer distance than just stopping. Braking and then turning in general won't work. Suppose I brake and slow down to a certain speed. Now I am a certain distance away from…
rallain | August 13, 2010We (Southeastern Louisiana University College of Science and Technology - but it should be called Science, Technology and Math) just had our fall convocation. Normally, we would share departmental news (which we did) and introduce new faculty. There are no new faculty and haven't been any new hires for quite some time now. Anyway, there are some things to report.
First, no one (not even the Dean) knows what is going to happen. No news is good gnus?
The LA Grad Act: This is a Louisiana state thingy that basically says we need to increase graduation rates. Here is the official site for…
rallain | August 13, 2010You know I have trouble letting stuff go, right? I am still thinking about these crazy long basketball shots. Here are some more thoughts.
Really, there are two things I am interested in. First, commenter Scott Post suggests that the drag coefficient might be around 0.25 instead of 0.5. I don't know. For the discussion before, it doesn't really matter. My point was to see a numerical model for a falling ball would be similar to the time and distance from the video. Changing the drag coefficient to 0.25 gives values that are still close to the video. So, I still think the video is real…
rallain | August 12, 2010There is something I am working on that will need some type of angle sensor. I am going to use a potentiometer. First, who came up with that name? Isn't this name the same as a voltmeter? Something is wrong with that name. How about we just call it a variable resistor or something like that?
These things are pretty easy to find if you have some old electronic stuff. Here is one I found in our "junk room".
This one was used in a lab as a variable resistor with plugs built in. The normal potentiometer has three connections; one for each end and one for the variable position in the…
rallain | August 12, 2010There is this commercial that has been coming on lately showing some people reading the Kindle at the beach. Why is this a selling point? It has to do with the way the Kindle works compared to something like the iPad. I would take a picture, but I have neither of these devices. Instead, I will make a diagram.
Maybe you can't tell from my diagram, but I am using the black rays to represent light reflected from the Kindle and red rays to represent light produced from the iPad. And that is the key. The Kindle does not have a light source, it is very similar to a piece of paper. The iPad…
rallain | August 12, 2010This summer I taught the part II of algebra-based physics. It is odd, but I rarely teach this course. I usually end up teaching the calculus-based version (with Matter and Interactions). There is something strange. If you look at the algebra-based physics I and calculus-based physics I, they are just about the same course. Both essentially cover forces, momentum, energy, and angular momentum. Oh, I know - some also cover waves and pressure and sound and stuff.
I think what tipped me off to the big difference in the algebra-based physics II is the theme in Matter and Interactions. Yes,…
rallain | August 11, 2010I am not a boy scout, but I still believe it is a good idea to be prepared. What to prepare for? Well, in Louisiana, it is the time to prepare for hurricanes and the looming budgetpocolypse.
Hurricanes
First, the hurricanes and tropical storms.
Model image from Weather Underground - best place to track storms (in my opinion).
This is pretty simple. Here is what I need to do:
Make sure my generator works and I have gasoline
Fill up the cars with gas (in case we want to leave)
Back up data and stuff
Pick up all the toys and stuff in the yard
Flashligh
Beer
That should do it. Of course…
rallain | August 9, 2010Here is a quick one. One of the big news stories recently was this regarding WikiLeaks and the release of the Afghan War Diary. There could be tons of things to discuss regarding this - but I am not going to do that. The first thing that struck my mind was "over 91,000 documents". That seems like a lot.
If each one of these documents were printed on one page, how big would the stack of paper be?
I could just estimate this - fermi-problem style. But instead, I thought would use a stack of paper. Here is a pack of 500 sheets of paper.
Opening it, I can measure the thickness:
How thick…
rallain | August 7, 2010I have seen several videos similar to this.
Real? Fake? How many tries did this take? Let the analysis begin. Before I do any analysis, let me state that I think this is not fake. I do not know that for sure, just my first guess.
How would I tell if it is real or fake? This is tricky. I can't really get a good trajectory of the ball to make some measurements on it because of the camera angle (next time people, make sure you set the camera up perpendicular to the plane of motion and far enough away to avoid perspective problems - thanks!) Really, the best I can do is to look at the…
rallain | August 5, 2010This is a classic problem. You are in a car heading straight towards a wall. Should you try to stop or should you try to turn to avoid the wall? Bonus question: what if the wall is not really wide so you don't have to turn 90 degrees?
Assumption: Let me assume that I can use the normal model of friction - that the maximum static friction force is proportional to the normal force. Also, I will assume that the frictional coefficient for stopping is the same as for turning.
Stopping
I am going to start with the case of trying to stop. Suppose the car is moving towards the wall at a speed…
rallain | August 4, 2010First off, I think this is a really good post (not this self-referring post, but the post I am about to link to)
Steak Dinner by Alemi at The Virtuosi
In short, this post is about cooking steak and the measurements of the temperature of the meat. Why do I think this is a good post?
First, it is just some ordinary everyday event (well, it's not everyday you get steak). The awesomeness just comes from saying "hey, maybe I should plot this temperature data".
If the post was just about plotting data, it wouldn't be terrible. But it does something else. It tries to fit this data to some sort…
rallain | August 3, 2010I am seriously late on this stuff. First, by clickers I mean student response systems. In a previous post, I stated how much I like these things. The basic idea (in case you have never heard of them) is that these are small devices that students in a class have. The instructor (learning facilitator) presents some multiple-choice questions and the students click a button to represent their answer. The summary of the student responses can then be presented to the class.
Big whoop you might say. But it is a big whoop and here is why:
Technologically and logistically, these are trivial to…
rallain | August 3, 2010You thought I was going to talk about a problem that math teachers could use, didn't you? Well, maybe math teachers can use this. (note: when I say "teachers" I really mean "learning facilitators")
It all started when I read this valedictorian speech from Erica Goldson. Here is part of it:
"I am now accomplishing that goal. I am graduating. I should look at this as a positive experience, especially being at the top of my class. However, in retrospect, I cannot say that I am any more intelligent than my peers. I can attest that I am only the best at doing what I am told and working the…
rallain | August 2, 2010
Try to say that 5 times really fast. Go ahead, try it. Well, at least it is not as difficult as Fox in Socks - man that book is a killer.
This WAW is basically a means to embed Wolfram Alpha queries into a webpage. Pretty cool idea, but I am not sure how well it does the job. In fact, I have tried to embed calculations in my posts before. So, how about I just give a quick review of some different ways to do this. For all these methods, I will put in a calculator to determine the density of something given its mass and volume.
Javascript version
Density calculator
Enter the mass:
kg…