Rhett Allain
rallain
Posts by this author
November 22, 2008
One of things I like to think about in science is "how do we know that?" It is interesting how one thing builds on another. This is a story of how the Greeks estimated the distance from the Earth to the Sun (an important idea in the development of the model of the solar system). I like this story…
November 20, 2008
Georgia Tech is playing Miami (not the real Miami, the other one Miami Florida). Right after a commercial, the camera shows this sign from a student (or just person) at the game:
(Sorry if the image isn't that…
November 19, 2008
Rarely am I up late enough to watch the Colbert Report, but by chance I saw it last night. I know Stephen Colbert is a big fan of Dot Physics, and so this is a message to him. Stevie, good job. Here is what he said during his show on the "The Word" segment. Just to give you the context, he was…
November 18, 2008
Big trucks are not as popular as they used to be, but gas prices are going down so maybe this commercial for the ford F-150 will start showing up again:
They say its a real demonstration, but it has seemed odd to me. (they also say this is a professional driver on a closed course and don't try this…
November 18, 2008
This must have been mentioned in a previous post, but I am too lazy to search. Anyway, I think have enough stuff here (at blog.dotphys.net) to finish moving stuff from my previous version of the blog. What does this mean and why do you care? You care because if you are one of the two people that…
November 17, 2008
Atwood's machine is the name of a device that looks like this:
Also known as "two masses on a pulley". Surprisingly, this simple device comes up a lot in intro physics texts. It also brings up some interesting issues. I will go over the basic way to solve a problem like this (as an example) and…
November 14, 2008
Here is a video of a guy jumping 35 feet into a pool of water only 1 foot deep.
UPDATE: Apparently, that video went away. Here is another version.
How does this work?
I don't think I even need to do a video analysis of this motion, all the important info is given. I will assume that air…
November 12, 2008
Numerical calculations are grand. Of course, they are just another form of normal calculations - like I have said before. So, I have mostly used [VPython](http://vpython.org) for my calculations on my posts. But there is a new game in town: [Easy Java Simulations](http://www.um.es/fem/Ejs/).…
November 11, 2008
[In part I of this post](http://scienceblogs.com/dotphysics/2008/11/interaction-between-light-an…), I struggled to show that a particle in an infinite well can only exist at certain energies. If you try to put a particle with more than one energy, the probability oscillates at a frequency (E2 - E1…
November 11, 2008
One of the fundamental aspects of physics is the study of light and how that interacts with matter. I have been putting off this post - mainly because I am not a quantum mechanic (I am a classical mechanic). There are lots of things that could be done in this post, but I am going to try and keep…
November 7, 2008
On MythBusters this week, Adam and Jamie tested the bullet-proofness of various objects. The one that sticks in my mind is the ipod. The said there was a report of a solider being shot by an AK-47, but he was saved because the bullet hit his ipod. To test this, Adam shot an AK-47 at an ipod and…
November 6, 2008
I just watched two episodes of the discovery show [Time Warp](http://dsc.discovery.com/tv/time-warp/time-warp.html). Really an interesting show. There are many videos that I could see some analysis project for (too bad I am like 20 projects behind schedule - I think of things faster than I can do…
November 5, 2008
[Here is a LiveScience article on cars that run "mostly" on air](http://www.livescience.com/technology/081103-air-car.html). I also hear students talking about this - how the world will change when cars run on air. This is misleading. These cars do not really run on air. It is not like you put…
November 4, 2008
**Pre Reqs:** [Work-Energy](http://scienceblogs.com/dotphysics/2008/10/basics-work-energy.php)
You need to be familiar with work and energy to understand this. If you are not familiar, look at the pre requisite link. Ok? Now, let's begin.
Suppose a ball moves from point A (3 m, 3 m) to B (1 m, 1…
November 1, 2008
I have been meaning to post something useful lately, but I am currently at the southeastern section of the APS. Anyway, I saw [this link on digg](http://www.hyperevo.com/new%20site/index.php?subaction=showfull&id=1225…)
Apparently there is a message in the source code on the digg page. Funny…
October 29, 2008
I don't need to explain that I think the Mythbusters are awesome (do I?). I just finished watching their latest episode. In it, they tested the scene from Indiana Jones and the Last Crusade where Indy puts a flag pole in another motorcycle wheel. The result in the movie is that the motorcycle…
October 28, 2008
Yes, I did some experiments with [Fantastic Contraption](http://fantasticcontraption.com/) ([Water sticks in Fantastic Contraption](http://blog.dotphys.net/2008/10/water-stick-springs-in-fantastic-contra…), [Torque from rotating balls in FC](http://blog.dotphys.net/2008/10/torque-produced-by-balls-…
October 28, 2008
Here is what is cool about [Fantastic Contraption](http://fantasticcontraption.com/) - it's like a whole new world, a world ready for exploring. I am Newton, and I can see if this world follows the models that I propose.
In this post, I am going to explore the elastic nature of the "water-sticks…
October 26, 2008
The fun part about exploring the physics of [Fantastic Contraption](http://fantasticcontraption.com/) is coming up with new setups to test ideas. Torque is not too difficult to set up. Here is what I did:
…
October 23, 2008
One of my students showed me this game, [Fantastic Contraption](http://fantasticcontraption.com/). 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…
October 23, 2008
I am sorry to point this out, but I can't help it. My kids watch this show "Fetch with Ruff Ruffman". It's mostly an ok kids show. However, there was a problem. In one episode, some kids were in the desert and measuring temperature with (they said it several times and it was even a quiz…
October 21, 2008
[In a previous post, I talked about numerical calculations](http://scienceblogs.com/dotphysics/2008/10/basics-numerical-calculation…). The basic idea is to use the momentum principle and the following "recipe":
Update the position of the particle
Update the momentum of the particle
Update the…
October 21, 2008
I know I should just let go, but this is what makes me, me. I understand that there are terms in physics (like for instance 'pressure') that are used in all sorts of ways in common language. The problem is when someone tries to explain something scientifically and misuses a word. Pressure means…
October 20, 2008
**Pre Reqs:** [What is a Force](http://scienceblogs.com/dotphysics/2008/09/basics-what-is-a-force.php)
[Previously, I talked about the momentum principle](http://scienceblogs.com/dotphysics/2008/10/basics-forces-and-the-moment…). Very useful and very fundamental idea. The other big (and useful)…
October 17, 2008
This is not a "fix-it" blog. However, I think the Internet should be a useful friendly place. Think about the times you have had a problem. The Internet has been there for you - right? I remember not too long ago, I was trying to set up iChat video chat with my brother-in-law and his brand new…
October 16, 2008
Maybe you know I like numerical calculations, well I do. I think they are swell. [VPython](http://vpython.org) is my tool of choice. In the post [Basics: Numerical Calculations](http://scienceblogs.com/dotphysics/2008/10/basics-numerical-calculation…) I used vpython and excel to do something…
October 14, 2008
**Pre Reqs:** [Kinematics](http://scienceblogs.com/dotphysics/2008/09/basics-kinematics.php), [Momentum Principle](http://scienceblogs.com/dotphysics/2008/10/basics-forces-and-the-moment…)
What are "numerical calculations"? Why are they in the "basics"? I will give you really brief answer and…
October 13, 2008
I went home for lunch today. While waiting, I saw this lizard. We have many lizards in Louisiana, I like them, really I do. So, this is what I did:
No lizards were harmed in the filming of this video.
I was really surprised. I thought for sure that I had tried this before and nothing…
October 13, 2008
There is this show "Weapon Masters" - I think it comes on the discovery channel. It is not a bad show. The basic idea is that they have this history guy talk about the historical aspect of some type of weapon and this other guy tries to make an improved version. Last night the goal was to…
October 9, 2008
**Pre reqs:** [Free Body Diagrams](http://scienceblogs.com/dotphysics/2008/09/basics-free-body-diagrams.php), [Force](http://scienceblogs.com/dotphysics/2008/09/basics-what-is-a-force.php)
The time has come to look at things that are NOT in equilibrium. The most basic question to ask yourself is…