rallain | March 6, 2009Temperature is a pretty weird thing if you think about it. How do you best define temperature? Let me go ahead and give you my favorite definition:
Temperature is the thing that two objects have in common when they have been in contact for a long time.
Yes, that is a good definition. Maybe now you can see why temperature is weird. Doesn't it have something to do with energy? Well, something - yes. Let me take an example. Suppose pour some hot coffee into a paper cup (I use paper because styrofoam(TM) is trademarked). Further suppose that this is super hot coffee from McDonald's. Can…
rallain | March 4, 2009Some time ago, I wrote about the awesome things the Greeks did in astronomy. Basically they calculated the size of the Earth, distance and size of the moon and distance and size of the sun. The value obtained for the distance to the sun was a bit off, but still a bang up job if you ask me. (where bang-up is meant as a good thing) If the greeks were in my introductory physics lab, they would need to include uncertainties with their measurements. What would the uncertainty in the final value look like?
In my introductory physics lab course, I have students measure things and estimate the…
rallain | February 28, 2009This idea comes from my friend Thomas. His son is like mine in that they both think LEGO are awesome, and they are correct. For some reason, Thomas decided to calculate the price per piece of LEGO in each set. To promote repeatability, I decided to do this also. Looking at the catalog at LEGO.com, I can get both the price of each set and how many pieces it has. Just a note, I looked at almost all of the Star Wars LEGO series and some other select themes. I didn't include any sets that had been marked down in price. I will put the first plot on down below, maybe this would be a good…
rallain | February 26, 2009First, I think we should all be using smaller lighter cars. They get better gas mileage, they are better for the environment and maybe even reduce traffic? (ok, not sure about that last one - but it is possible). In Buzz Out Loud 918, they were discussing Toyota working on new car bodies built from sea-weed based plastics (from a wired article). One point that was brought is the comparison between old plastic bodies (the pontiac fiero comes to my mind) and these new plastics that should be much stronger. Well, here is the problem. Light strong bodied cars can be dangerous. Really? Yes…
rallain | February 25, 2009I overheard this high school student complaining about a teacher. Here is essentially what she said (about a class her friend is in):
"This teacher is crazy. He said we have a test the next day and he gave them a study guide. But he didn't give the answers to the study guide. My friend and her mom stayed up till midnight looking up the answers on google."
I am pretty sure this was regarding a math class. So, what is the problem? I think there are a couple, but it mainly has to do with the nature of assessment. What is the point of assessing if students know (memorize temporarily) stuff…
rallain | February 24, 2009Basically, the title says it all. Here is a short tutorial on projectile motion calculations with a spreadsheet.
Record your screencast online
I left out a lot of details, so maybe these links will help:
Spreadsheet tutorial for numerical calculations (video)
More details on numerical calculations
Projectile motion
rallain | February 24, 2009Quantum mechanics is not my area of expertise. Really, I have no area of expertise. However, I think it is time to bring the whole photon thing back up. Yes, I know I was a little harsh before. Maybe I should start over.
First, models. Yes models. I think science is all about models. Scientists build models that attempt to agree with observations. These models could be mathematical, physical, conceptual or numerical (like a computer program). For example, take Newton's Law of gravity (which isn't really a law). It says that the gravitational force between two objects has the…
rallain | February 21, 2009This is one of my favorite demos. Easy to do and doesn't really require any equipment. The basic idea is that you support a meter stick horizontally with two fingers. Slide your fingers in and they will both meet at the center of mass. Here is a video.
Meterstick friction demo from Rhett Allain on Vimeo
So, how does it work? To explain this, you need to understand friction and equilibrium. Well, nobody really understands friction - but anyway..
First, what is equilibrium? Equilibrium means that an object's motion does not change. For this case that means that both it's velocity and it…
rallain | February 19, 2009After talking about textbooks, commenter Kevin posed the question: which would cost more, printing out a free book or reusing a purchased textbook. Great question. How about some quick estimation (some of this stuff I have no clue about). First, how much do high school textbooks cost? Probably the most popular is Glencoe Physics: Principles and Problems. Amazon lists this for $95.55 (which I will call "about a hundred dollars"). How much do schools pay for this? I have no clue. I imagine if a whole state adopts it, they can get some deal. Maybe they could get it for $50 a copy.
How…
rallain | February 19, 2009I saw this some time ago, probably in The Teaching Professor online magazine thingy. The basic idea is to leave your class alone when they are having a discussion. I have done this a couple of times. Yesterday was the first time this semester. Here is the deal. In this class (Physics for Elementary Education Majors), they collect evidence and build models. For that day, the experiments were giving students evidence about what happens to a fan cart when the strength of the fan changes and what happens when the mass of the cart changes.
When it came time to discuss the ideas, I made sure…
rallain | February 17, 2009I previously talked about textbooks and how there is clearly a problem. The CK-12 Foundation is trying to do something about this problem with the flexbook. Basically, the flexbook allows teachers to create their own text by combining different free content. You can customize a book that closely meets the needs of the class.
I think this is a great step in the right direction. One problem that immediately popped into my head was "how would a high school teacher get this approved?" Someone at the conference (he didn't have a name badge on) said "well, I am old enough, I just do whatever I…
rallain | February 17, 2009The first thing from AAPT that I would like to mention is SAM Animation that Brian Gravel demonstrated. SAM is free software that allows for the easy creation of stop motion animations. Basically, you use a web camera to take successive pictures and put them together as a movie. The software includes features (I think they call it an onion view) to see your previous frame while you are making the next frame. I think the software also lets you do time-lapse videos (which I think are awesome but they take lots of patience).
Fine, it is cool, but what do you do with it? Besides make movies…
rallain | February 17, 2009A quick note. I am back from the AAPT meeting in Chicago. My first surprise was from my hosting company (lunarpages). They said that I had once again gone over my CPU usage for my site. I am really not sure why and I can't really see my CPU usage. Anyway, the short story is that I either have to upgrade my service or move to another hosting company. Does anyone have a hosting company they could recommend? I will probably just stay with lunarpages because I don't have time to mess around with moving.
Another note, I am going to give a few summary posts of some of the awesome (or…
rallain | February 15, 2009Someone complained about a teacher using this question and the answer was disputed. After some time, the teacher claimed that the answer was that lightning is static electricity because she looked it up on the internet. So, I decided to look also, here is what I found searching for "what kind of electricity is lightning?" in google:
Electricity Facts - Dialogue for Kids (Idaho Public Television)
A couple of complaints about this site:
First, I am not fond of the term "Science Facts". What is a science fact? Something that is proven true? This really is not how science works.
Second, I am not…
rallain | February 13, 2009The local Society of Physics Students invited me to watch the movie Sunshine and then participate in a post movie discussion. There was one thing in the movie that really got me. Of course the movie made many of the common space mistakes. But this one didn't seem necessary. Let me outline this part of the movie (I guess I should say spoiler alert - although this isn't central to the main plot). Here are three frames of a comic I drew to reproduce the scene.
After watching Sunshine, the astronauts try to go from one ship to another without space suits (well, one of them had a suit).…
rallain | February 12, 2009Previously, I talked about science fairs. One of the problems is that students don't really have a good understanding of data analysis. For me, statistical analysis is just something to do with data. It isn't absolutely true. So, it doesn't really matter that students use sophisticated tests on their data. The important point is they use some type of test to compare data.
I just made up some arbitrary data analysis rules. Maybe if students and judges accept something like this, it could really improve science fair projects and judging.
To explain my analysis, I decided to have my own…
rallain | February 12, 2009Since this could be current events, I am reposting my analysis of space debris in the movie Wall-E.
Here is a shot from the scene where the space craft is leaving Earth:
In this scene, the spacecraft has to break through all the Earth-based space debris. The first problem is that the unused satellites are just sitting there. If they were to stay in orbit, they must move. Maybe the WALL-E creators are sticking with the no air means no gravity idea. At least they are consistent.
The other problem with that scene is the sheer amount of junk in orbit. Suppose that was 300 km above the surface of…
rallain | February 10, 2009Last friday I volunteered as a science fair judge. It took half a day, but I did get free food and tons of things to blog about. There are so many things to say about science fairs that I don't really know where to begin. I actually might not even address all the issues. Here is what I would like to talk about (in no particular order):
What is the purpose of a science fair?
How do you win a science fair? Tips.
What about judging? Are the normal methods reliable?
Data Analysis tips for middle schoolers
Creativity vs. the Internet vs. parents.
Social Science Fair posters? Er?
Why science…
rallain | February 7, 2009A couple of commenters expressed concern over the use of centrifugal force after my rant on the use of the word force. So, what is the deal with these two terms? Are they ok to use? Are they real forces?
First, are they real forces?
It depends on what you mean by real. What is a force? Here is a quick overview of what a force is. I previously talked about real vs. non-real forces. For me, I say that if the force is essentially one of the 4 fundamental forces then it is "real". With this definition, centripetal force would be real and centrifugal not real.
Centripetal Force
Centripetal…
rallain | February 4, 2009Not sure if you know what Jump the shark means. I figured it was a common term. Here is the wikipedia entry. Or maybe you would like a graphic explanation. Here it is:
So, why the attack on textbooks? The main reason is that I just posted a rant about forces (or abuse of the word force) and I am going for the combo attack (more points that way). Actually, this has been in my mind for quite some time. There was a post on Uncertain Principles that started me thinking about it again.
I have been afraid to really speak my mind on this issue because I don't want to completely enrage the…