Rhett Allain
rallain
Posts by this author
September 14, 2008
**pre-reqs:** trig
Think of the following two things. Temperature and wind speed. These are two different things that you could measure, but there is one big difference. Wind speed has two parts to it - how fast and which direction. Temperature is just one thing (no direction). Temperature is…
September 14, 2008
Can you believe it? Have you seen this video?
Are you thinking what I am thinking? WOW. How could these people not follow my rules for cool internet video. Once again, here they are:
1Keep the camera stationary. This way I don't have to keep moving the origin in the movie.
2Don't Zoom. Same…
September 14, 2008
I am sure I mentioned that I am moving to WordPress (from Rapidweaver). I would like to have all my important posts moved. To do this, I am just going to repost them in WordPress. Maybe there is a better way, but I am not sure. So, the point is that if you have been reading this for a while,…
September 14, 2008
Friction in Line Rider
Is there friction in Line Rider? Does it function as physics would expect? To test this, I set up a simple track:
Basically, a slope with a flat part to start with and to end with. Let me…
September 13, 2008
There is no air resistance in line rider. Sorry to spoil the suspense.
To test for the presence of an air resistance force, a track was created that let the rider fall.
(note the markers on the side.…
September 13, 2008
Scale of the Line Rider
First, we assume that the line rider is on Earth and for low speeds will have a free-falling acceleration of 9.8 m/s2. Next, an arbitrary distance is selected. In this case the length of the sled is chosen to be 1 LU (Linerider Unit).
![line rider](http://scienceblogs.com/…
September 13, 2008
Part I: Introduction
http://linerider.com is a flash "game" in which the user can create tracks. A rider is then allowed to slide down these tracks. If you have not played this, I recommend you DON'T play it. It is very addicting and can consume many hours of your time (hours you would otherwise…
September 12, 2008
Suppose I am working on a problem and I wish to calculate the density of something. I measure the mass to be *m* = 24.5 grams and the volume is *V* = 10 cm3. In this case the density would be:
ALERT! ALERT! ALERT…
September 11, 2008
The MythBusters aren't really doing it wrong, but they give me a chance to talk about some physics. In the latest show, they tested the myth that two phone books with their pages alternating were indestructible. To test this, they put the two phone books together and then pulled them apart in a…
September 8, 2008
My kids like books. Especially when they are going to bed. I let my daughter pick a book and she picked "Clam-I-am. All About the BEACH" by Trish Rabe. It is nice, it rhymes. The pictures are pretty. Then I get to this page:
. My wife convinced me to go out and hear this band since we are staying at my parents and they said they would watch the kids. In general, I am way too old and crotchety to go out…
September 5, 2008
**pre-reqs:** [kinematics](http://scienceblogs.com/dotphysics/2008/09/basics-kinematics.php)
My previous "basics" post was on kinematics (in one dimension). But what about two dimensions? In particular, what about projectile motion. My motivation here is that I was about to talk about analysis…
September 4, 2008
One of my daughters was just reading Chicken Little to me. I don't know if you are familiar with Chicken Little, but she is a chicken that runs around telling people "The sky is falling". In my normal fashion, I started thinking about the plausibility of this. What would fall? What would you…
September 3, 2008
**pre reqs:** *none*
Often I will do some type of analysis that I think is quite cool. But there is a problem. I keep having to make a choice. Either go into all the little details, or skip over them. My goal for this blog is to make each post such that someone could learn some physics, but I…
September 2, 2008
Here I am, at my parents house. There is no power at my house and Louisiana in September with no power is really a whole bunch of no-fun. But maybe I can use this time to talk about science.
**The Nature of Science**
Here is a review. What is science all about? (I am pretty sure I talked about…
August 29, 2008
I teach classes. I ask questions in class. I wait for answers. All faculty do this, so who cares. If you are in a class or teaching a class, how long do you wait for someone to answer your question? Well, I asked two questions of my class this week.
1. Estimate how long I wait when I ask you…
August 28, 2008
I recently saw a comment on a blog somewhere about putting satellites into space (I think it was from a post about a rocket that blew up). The poster suggested using a giant catapult to put things in space instead of rockets. Maybe he or she was kidding, or maybe not. But I have heard this idea…
August 27, 2008
Maybe you can tell I am watching the MythBuster's Moon Special. In the show, the MythBusters go in a plane to reproduce the gravitational forces on the moon. I previously went over this, so here is the link:
[Tutorial on how gravity and weightlessness (zero-g) work](http://scienceblogs.com/…
August 27, 2008
Clearly the MythBusters did this before I did (it's just airing tonight though). I just wanted to say that I posted some videos of the Apollo "jump salute" video analysis and also sped it up to "Earth-like" accelerations. I then made a video of my daughter doing the same thing on Earth and slowed…
August 26, 2008
Heat. You have heard it before. You have used it. I have even used it. Do we need this word? No. Is this a useful word? No.
Let me start with the definition as usually stated in a physics type text: (this is from [dictionary.com](http://dictionary.reference.com/browse/heat))
*heat:* a…
August 26, 2008
I know the olympics are basically over. Really, I should have posted this earlier. Anyway, the gymnastics feat that always impresses me is the Iron Cross (I think that is what it is called). I know you have seen this, but here is a picture from wikipedia:
![Example 2ofironcross](http://…
August 25, 2008
Dear RapidWeaver,
What did I do to you? I like you, I really do - but this is why we broke up. It's not you, it's me. No wait, it's you. I am looking back through my old dotphys posts and most of my introductions are GONE. I was starting to think I was crazy when I wrote these. Take for…
August 24, 2008
I can't believe there is still all this talk about what to call Pluto. Can't we just move on? In an effort to help, I have summoned the Zombie Feynman to get his words on the subject. This is what he said:
"We (my father and I) used to go up to the Catskill Mountains for vacations. In New York…
August 23, 2008
As you may or may not have noticed, I have been using RapidWeaver for my blogging posts. (if you don't know what that is, it doesn't matter) Anyway, I think my stuff was getting a little too big for that software. It was a great place to start, but it is time to move to something else (WordPress…