Rhett Allain
rallain
Posts by this author
November 10, 2009
Maybe this isn't that mysterious. However, quite some time ago my daughter found this rock in the backyard. First, you must understand that this is an odd occurrence. In this part of Louisiana, there really aren't any rocks, just dirt. When she showed it to me, I readily dismissed it as some…
November 10, 2009
This is for commenter JimP. How do you take into account uncertainty when using video analysis? A great question. The first thing to think about is where does the uncertainty come from? My first guess would that it would be from the user. Where does the user click? Is it right on the object…
November 5, 2009
Very simply, parallax is an apparent motion of an object due to a change in observation position. Let me start with an example. Here are two photos. I took a picture of the cabinet in the background from two slightly different positions. In the foreground is a clone trooper that did not…
November 4, 2009
I already attacked the 2008 Punkin Chunkin Show. So, now I going to give the chunkers some tips. In case you aren't familiar, the Punkin Chunkin contest has teams create devices to launch a pumpkin. They have different categories, but I am going to focus on the air-powered devices. The basic…
November 2, 2009
I am sad to say the following comes from a school that I attended. This was from an alumni newsletter regarding the activities of one of the physics faculty.
"Since the time of Archimedes, sciences advanced along two avenues, through new experiments and through theory...."
I have a problem with…
October 31, 2009
Here is the deal. Why would you put a lot of effort into explaining something wrong? I just don't get it. Wouldn't it be easier and better to just not say anything? The particular show I am ranting about is the 2008 Punkin Chunkin on Discovery (I think). Fairly ok show, but they should have…
October 30, 2009
In the past couple of weeks, we have had two different publishers 'pitch' their online homework system. First, they are fine people and interesting products, but I just don't think this is going to work.
Online Books
I think the publisher's plan is to have a textbook, and offer extra stuff to go…
October 27, 2009
I know I saw this demo somewhere. Maybe it was at an AAPT conference a few years ago. I have always wanted to build this, but never got around to it. Until now. Here is the demo (it is easy, you should make one too)
So, how does this work? I think the simplest explanation is that the drinks do…
October 24, 2009
Sometimes it is difficult to come up with new labs. Ideally, a lab should show use some of the basic physics principles as well as have something the students can measure. What to do with circular motion? I don't know how I forgot this, but here is a lab I used to do as an undergraduate student…
October 21, 2009
My friend Konrad showed me this awesome toy he made.
I know it doesn't make sense yet, so let me explain. Basically, you take this marble and roll it down the tray through the pegs. The pegs sort of randomize where the marble rolls through the hidden section. Inside the hidden section, it looks…
October 20, 2009
I don't really know what that title actually means. So, I have been having problems with my PASCO projectile launcher devices. I will just call them launchers (they are really cannons). In my previous post, I looked at the launch speed from a launcher shot horizontally and vertically. The…
October 15, 2009
The basic idea of the student response system is that each student gets some electronical (or not - see below) device that lets them answer multiple-choice questions. (Science Geek Girl has a good summary of clickers also) A computer then displays the distribution of responses for the class.…
October 13, 2009
The last time I looked at this projectile motion lab, I was confused. My different methods for measuring the launch speed of the ball were not even close to being consistent. So, I am bringing out the big guns - video. I made a video of the ball shot both horizontally off the table and…
October 12, 2009
I put together this short presentation on fake videos for a class. What the heck, I will also put it online so that maybe some other people can use it. So, here it is. I have it in many forms. First, a video of me going through the talk. Then I have the keynote and PowerPoint files with the…
October 11, 2009
The other myth the MythBusters looked at last week was the phrase "knock your socks off" (along with the dropping and shooting a bullet myth). But before that, let me complain.
Maybe it is just me, but I totally cringe when these guys use the word 'force'. Force probably isn't the best term to…
October 9, 2009
If you didn't catch the latest MythBusters (yeah! new episodes), they did something straight from the physics textbooks. Just about every text has this example of shooting a bullet horizontally and dropping a bullet from the same height. The idea is that they should hit the ground at the same…
October 6, 2009
Many textbooks are pumped up about Newton's 3 laws of motion. For me, not so much. First, (as many other's point out) these are really Newton's ideas about force. Second, the first law is pretty much a special case of the second law. Here are the first two laws (in my words):
Newton's First Law…
October 6, 2009
You know I like demos, right? This one is quite fun to do even in a class. The basic idea is to take a bucket of water and swing it around in a circle over your head. Simple, but if you have never done this one, it can be a little intimidating. Here is an example.
Water Demo from Rhett Allain…
October 4, 2009
There were a couple of things that bothered me about the MythBusters' myth where they fired bullets in the air. The myth was that a bullet fired in the air could kill you. The first problem is that it is not a myth. There are several reported cases of people being killed from bullets that were…
September 30, 2009
This is really a lab that I have students do, but I am pretty sure they don't read this blog - so it is ok. If they are reading this, hi!
We have these projectile cannons that shoot small balls. In order to look at projectile motion, they need to first determine the launch speed of the ball. I…
September 29, 2009
I was shocked. After installing Mac OS 10.6 (Snow Leopard) Tracker Video Analysis didn't work. This is one of my favorite programs for blogging.
It appears that the problem is with 32 bit Java vs. 64 bit. I don't really understand why one doesn't work, but Tracker doesn't work with 64 bit Java…
September 28, 2009
I think we are entering a new era. An era where it is quite simple to find and get great videos. Oh, just saw a great tackle on the TV? In the old days, you would have to get that video off the TV yourself. Not anymore. Welcome to the interwebs. Also, the quality is awesome compared to 10…
September 23, 2009
You know I like the Mythbusters, right? Well, I have been meaning to look at the shooting bullets in the air myth for quite some time. Now is that time. If you didn't catch that particular episode, the MythBusters wanted to see how dangerous it was to shoot a bullet straight up in the air.
I am…
September 21, 2009
Thanks to all who participated in the Dot Physics Census. Let me share some of the things that I learned:
The survey was flawed. How dumb was I? Almost everyone would fit into more than one of those categories. Oh well.
Google Docs makes pretty good surveys. I made a form in google docs and…
September 17, 2009
This is Tom's fault (Swans on Tea). He suspects that most of the physics blogs are read by physics bloggers.
I have kind of been avoiding this, but I guess I need to know who my readers are. Actually, there are two groups of readers - regular readers and googlers. So, who are you?
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September 17, 2009
Yes, this can be very complicated. But what should a middle-school student understand about light? You see stuff in textbooks that is either wrong or just a bunch of disconnected factoids (I like the word factoid). So, what do I think is important about light (not at the Maxwell's equations…
September 16, 2009
The administration are people too. I just want to start off saying that. However, in this case, I just don't get it. The more I think about it, the less I get it.
Here is the plan our administration came up with. Faculty will report class absences for every Tuesday and Wednesday course. Absence…
September 15, 2009
As I said before, I went a SPIN-UP workshop (you can find tons of info and the SPIN-UP report here). The basic idea of the SPIN-UP program is to first look at schools that are successful in their production of undergraduate physics majors. And with an understanding of what makes them successful,…
September 14, 2009
I really shouldn't do this. I might be helping someone to set up something dangerous. But, I am going to anyway. Here is a question posted on some forum. (actually, it is from math help forum)
"I'm anticipating a good winter this year, one with lots of snow. My yard is sloped quite a bit and it…
September 9, 2009
This weekend I am off to a SPIN-UP (Strategic Programs for Innovations in Undergraduate Physics) meeting. The basic idea is for physics departments to meet and discuss how they can be better. Note: if you don't have a good acronym, you don't get any funding. In preparation for this meeting, I…