Rhett Allain
rallain
Posts by this author
December 26, 2009
On a previous episode of The MythBusters, Adam and Jamie made a lead balloon float. I was impressed. Anyway, I decided to give a more detailed explanation on how this happens. Using the thickness of foil they had, what is the smallest balloon that would float? If the one they created were filled…
December 25, 2009
So, analysis of the movie Up is pretty popular in the blogosphere. Figure I might as well surf the popularity wave. So, I have a couple more questions.
The most important thing to estimate is the mass of the house. I am going to completely ignore the buoyancy of the house. I figure this will be…
December 24, 2009
Which wastes more fuel? (and thus produces more carbon dioxide). This is a difficult to question to answer for a variety of reasons. The main reason is that a speed change from 71 mph to 70 mph is different than a reduction from 56 to 55 mph.
First, let me be clear that the question of how much…
December 23, 2009
One of my students showed me this game, Fantastic Contraption. The basic idea is to use a couple of different "machine" parts to build something that will move an object into a target area. Not a bad game. But what do I do when I look at a game? I think - hey! I wonder what kind of physics this…
December 22, 2009
I re-watched Harry Potter and the Order of the Phoenix last night and my wife and I noticed something about teaching. Of course I mentioned that this would make a good blog post (and she may still post it on her blog, but I can't help myself). If you have not read the book or seen the movie, I…
December 22, 2009
Haiku:
The daylight grows short
Blogging time is scarce for now
Repost is now here
I am ready. Bring on the comments about the proper way to write a haiku. Of course, I should warn you that I am technically a professional Haikuer - here is my winning entry to ThinkGeek's haiku contest
Here is…
December 22, 2009
Female Science Professor has been talking about student evaluations lately. (here are some other Student Eval posts - post 1 post 2 post 3). I had some ideas on student evaluations, and here they are.
One Question
A friend of mine likes to say that student evaluations should just be one…
December 20, 2009
This is one of my favorite demos. I like it because anyone can do it at home and people usually find the results surprising. Here is the situation:
How much of yourself could you see in a small mirror? What if you move farther away from the mirror, can you see more of yourself? If you want to…
December 18, 2009
Fight Science is an entertaining show. Great graphics. The basic idea is to look at the science in different fighting styles. They had a clip-style commercial on it during a MythBusters episode I was watching. And from that, I can say that the kicking looked cool, but the science needs some…
December 16, 2009
Maybe this could fall under my "physics of parkour". It could also apply to the MythBusters "dumpster diving" episode. In both of these cases, the question is: how far can you jump off of something and not severely hurt yourself. They do this a lot in parkour. Here are some examples:
There are…
December 15, 2009
Maybe you have noticed how much material there was (for me at least) in last week's MythBusters. One of the myths they looked at was the bus jumping over a gap in the road from the movie Speed. I am not looking at that myth, it has been discussed many times in many places. Rather, I am going to…
December 14, 2009
There was a question from Jerry in a previous post:
"A simple question for which I can't find an answer: Why do you have to collimate light spectroscopy? What would happen if you didn't collimate it?"
The basic idea of spectroscopy is to look at the different colors of light coming from some source…
December 14, 2009
The solar system is difficult to show correctly. Why? It is difficult because the size of things are vastly different. Let me use units common in solar-system astronomy, the Astronomical Unit (or AU). One AU is the distance from the Sun to the Earth. If I want to look at all the planets, I…
December 10, 2009
It is the end of the semester, and I hear stuff. A lot of this stuff I do not like to hear. This is a sample (essentially):
"I don't have to take the final in that class, the instructor said I just have to organize some folders instead"
"I got an A on all the tests, but the instructor said my…
December 10, 2009
This picture has been all over the blogs.
I don't want to talk about this picture too much - that has been done (a good summary discussion can be found at Bad Astronomy). Apparently, this is some type of rocket mistake or something.
Although the picture is cool, it is not as cool as this…
December 10, 2009
Have I not made it clear how much I like the MythBusters? Also, I am totally aware that they are not (nor do they claim to be) scientists. Really, this is what makes their show appealing (maybe?). So here is the problem now. And, it is not just the MythBusters - I see other shows making the…
December 9, 2009
This is a requested post. Clearly, I do requests. The idea here is that I am going to give all the details needed to determine the equation of motion (and then model it) for a basic pendulum. Warning: this post is a little more advanced than my normal posts. There are some prerequisites. You…
December 7, 2009
So, it snowed here (in Louisiana). Sure, it wasn't a lot, but it was still a big deal. The following day, there was still some snow on the house roofs. I took some pictures. Here is a shot looking at the North side of a house.
And here is a view of the South side of the same roof.
What is so…
December 6, 2009
Looking back at part I of this idea, I don't think I did a very good job. Let me summarize the key things I wanted to say:
Normally, there are two ways of modeling the motion of an object:
Calculating the forces on the object and using the momentum principle or Newton's second law (which are the…
December 4, 2009
This post has been sitting in my mind for quite some time. Really, it is about mechanics - not about pendulums. What is the goal in mechanics (classical mechanics, if you like)? Generally, it is to find out how something changes over time. If you could get an equation of motion, that would do…
December 3, 2009
I showed this demo in class and I was surprised at how cool the students thought it was.
They actually thought it was some kind of trick. It is not a trick. Instead, this is an example of the angular momentum principle. If you want to try this yourself, I guess you are going to have to find some…
December 1, 2009
One of the roads near my house was just redone. They added some awesome retroreflectors in the middle. Here is a shot. No wait, I don't have a picture of that. I tried to take one, but it just didn't turn out very well. Oh, you know what it is supposed to look like. It looks like little tiny…
November 30, 2009
I am moving to ScienceBlogs.com. So, as I have said before, basically it will be the same stuff, new server. As of right now, only my new stuff is at http://ScienceBlogs.com/dotphysics, but soon all my old stuff will be there too.
To summarize:
It is not you, it's me.
Thousand points of light.…
November 29, 2009
The more I think about the last MythBusters' exploding water heater, the more cool things I see. How about I look at the energy of the explosion. There are three things I can look at:
How much energy went into the water heater from the electric source?
How much kinetic energy did the water heater…
November 26, 2009
This year's episode of Punkin Chunkin is coming up (I think tomorrow). Discovery just showed a teaser commercial with the specifications for one team's machine. If you are not familiar with Punkin Chunkin (World Championship Punkin Chunkin), the basic idea is to project some pumpkins. (note, if…
November 25, 2009
I feel like a just came to a new school, or a new place. Well, I have migrated servers before, so this shouldn't be too bad. It really is nice to be here at ScienceBlogs. If you are unfamiliar with what I do, basically I can summarize:
Analyze stuff I see. This is usually from a TV show or a…
November 23, 2009
Everyone knows, or should know how much I like MythBusters. Here is the problem. Below is a picture of Adam analyzing the motion of a an exploding water heater.
Actually, I applaud Adam for his creative use of the vernier caliper. Really, it is an example of "making things work". However, in…
November 20, 2009
In my previous post on launching a pumpkin (punkin chunkin) I essentially just looked at what happens to the pumpkin after it is launched. How fast would you have to shoot it to go 1 mile? The answer seems to be around 1000 mph and they are currently shooting them around 600 mph.
The question for…
November 19, 2009
Last night I saw the newest episode of MythBusters. One of the myths they revisited was the exploding water heater. Well, it turns out that I had an analysis of this first explosion, but I didn't move it over when I switched software. So, here it is.
In case you never saw the first episode of…
November 13, 2009
Not really. Here are the details (and some data) for the Millikan Oil Drop Experiment without the oil drop that I talked about previously (originally from The Physics Teacher - lucky you, it was a featured article so it should still be available (pdf)).
The basic idea that Lowell McCann and Earl…