rallain | February 3, 2009People say I am picky. Ok, sometimes I am. But somebody has to stand up for what is right and just. Maybe I am that person.
Please stop using the word force if you don't know what it is.
There. I said it. You can attack me now.
It wasn't just one thing that got me fired up. It was two things. First, I read this article on physics and football (Physics of 'The Hit' from the NY Times). If it was just this article, I would have let it go and moved on. But no. One of my kids just happened to be watching MythBusters (We all love MythBusters) and there was a discussion that used the term…
rallain | February 2, 2009I enjoyed the super bowl commercials for the most part. You have to be careful not to have too high of expectations, or you will set yourself up for a big letdown. Here is a quick analysis of one of the commercials. This is a Bud Light commercial where at the end they throw a guy out of an office window because he suggests they save money by not buying beer. Are there any actual office meetings that serve beer? (Sorry if I spoiled the ending for you)
I am going to analyze the motion of the guy going out the window. Just because.
At some point in the future, I am going to make a short…
rallain | January 30, 2009I said I would come back to this, and I am. I am a man of my word. Yesterday, I posted a link to a video of this really cool water rocket thingy.
How does this work? What is the physics going on here? I think this can be best explained with the momentum principle.
Let me start by pretending like I have some object that shoots out a piece of water (or really it could be anything). Also, let me pretend like this is in space ore something where there are no external forces.
Above is a before and after picture. Initially, there is something (the box) with water inside. Through some process…
rallain | January 30, 2009Buzz Out Loud is one of my favorite tech podcasts. Unfortunately, I am a little behind in the episodes. However, in the episode 900 there was an email from a listener regarding LHC and black holes. The emailer claims that a massive black hole would mess up Earth's orbit. This is not quite true.
I was getting ready to make a lengthy post about how black holes work, but did a way more awesomer job than I could do. Stefan and Bee describe some very important points:
First, black holes created in the Large Hadron Collider are based on a theory that has not really been verified. So, it might…
rallain | January 29, 2009I saw this on Hack a Day, but I am sure it has been posted in other places also (seems like something that would be on Swans on Tea). Check it out.
Amazing New Water-Powered Jet Pack - Watch more free videos
Some pretty cool stuff. I am pondering the questions to be answered right now.
rallain | January 29, 2009I really didn't want to post this, but I am going to anyway. I used ScreenToaster.com to make a screen capture movie (with audio) of a tutorial on spreadsheets.
This should accompany my previous post on numerical calculations.
Free online screen recorder
rallain | January 27, 2009We have all seen the Kobe Bryant video of him jumping over an Aston Martin - this keeps coming up on the Internet. There has been vast discussions of whether this is real or fake. I will do my best to examine the evidence. In short (in case you don't want to read the whole thing) Kobe can most likely really jump that high, it is possible that there was some perspective trickery involved. Here is the video in case you are brand new to the WWW:
Oh - don't forget I already analyzed Kobe Bryant jumping over a pool of snakes. I voted that was real.
First, let me give a personal note to Kobe and…
rallain | January 27, 2009Should you grade on a curve or not? If you are student, the answer is clear: go by whatever the instructor does. Otherwise, you have a choice. I don't like to tell other instructors or faculty what to do because I respect their freedom. For my classes, there is no curve. Why? Well, the question really is: "why grade on a curve?" I don't know the exact reason for particular instructors, but I can come up with some possible reasons.
Curve for competition
This is a very common curving reason. The basic idea is that the class is a competition between the students. The strong survive.…
rallain | January 25, 2009When you pour a beer, there is this foamy top called the head. The size of the head decreases over time. What is this process dependent on? Clearly, little bubbles of beer are popping. Does each bubble have an equal probability of popping? Do only the bubbles on the top (or bottom) pop? I became aware of this idea from a colleague. Maybe he was going to do an analysis, but I haven't seen it yet. If you do (Gerard), I am sorry for doing this before you. This may have been investigated before, but in the spirit of re-doing everything I have not searched for previous beer head studies.…
rallain | January 22, 2009Question: When is the Sun directly overhead? (assume you are in the United States of America)
Common Answers:
Everyday at noon.
On the summer solstice (June 21ish)
Answer: For continental U.S. the answer is never. Since the Earth's rotation axis is tilted 23.5 degrees with respect to its orbital motion around the Sun, one would have to be less than 23.5 degrees above or below the equator to have the Sun pass directly overhead (once per year).
Here is a video I made over the course of a day in Louisiana. Note that it rains and then the clay softens the pen falls. At the end, my dog hit the…
rallain | January 20, 2009So, you are taking a college science course. Maybe it is physics, maybe it is chemistry, maybe its a lab. Either way, you always end up with these problems that involve unit conversions. You think you have the hang of it, but sometimes you make some mistakes. Here is my explanation for converting units.
Convert units? Me? Why? I have google. Yes, that is true, google (for the most part) does an excellent job at unit conversions. But....I doubt your instructor will let you use google on your test. Don't you think you should have a good idea of how to do it? Don't worry. Unit conversion only…
rallain | January 19, 2009I just can't pass this up. One of the chemistry majors had a complaint with the power company. After an unusually high previous power bill, they checked the electric meter half way through the month. The meter said they had used 90,000 kilowatt-hrs of electricity. That is a lot of energy. It is also a lot of money. If I estimate 10 cents per kilowatt hour (the prices varies in space and time), this would be a $9,000 bill.
So, what is the deal? Is it a broken electric meter? Could be. If it is not, maybe it is a short. Shorts usually blow a fuse, but if it were an older house, could…
rallain | January 18, 2009Podcasts are great. While cleaning the car today, I listened to a new one - Stuff you missed in history class (itunes link). In one episode, they were talking about alternative theories about early visits to America. There was some guy that was claiming the Chinese visited the new world 70 years before Columbus (or something to that effect).
This is a great example of how similar science and history are to each other.
Both science and history make 'models'. In history this may be 'the Chinese visited americas before the Europeans'. It is just like a model in science. It is an idea that…
rallain | January 16, 2009It has been windy here lately. Sometimes I think that is an ok thing. You see, when I ride my bike to work I am probably going to have the wind at my back for one of directions. It is great feeling like Lance Armstrong because of the boost you get from the wind. With a good wind at my back, I can almost keep up with the traffic (I would keep up if they went the 25 mph speed limit).
Of course, with a great boost comes a great drag. When I ride into the wind, I feel weak. I pedal as fast as I can and cars just whiz right by like I am standing still. When you are in a car, you don't…
rallain | January 14, 2009I just finished my first class of "Physics for Elementary Education Majors". The maximum size for the class is 32 students and it is very interactive. I make it a point to learn student names as quickly as possible. This is something I am terrible at.
Should you memorize names? If it is a reasonable size class, I completely recommend it. Even in one short class, I noticed a difference in the atmosphere by knowing all their names. Here are my criteria for memorize or not:
Class size less than 40
Meets more than once a week
Not just a plain lecture class
Well, those aren't really the…
rallain | January 13, 2009I was going to title this post "Blog-a-lama-ding-dong" but I read somewhere that the title should be very descriptive (for better search optimization). So, my brother decided to start a blog. He was looking for some direction. I am by no means an expert blogger, but I do have some ideas about blogging. But remember - not an expert. If you are serious, seek professional advice.
Below are some random thoughts, and observations from my slightly more than 1 year of blogging.
Oh - here is my brother's blog (lifeofajenius.blogspot.com). I am still not sure what it is about, but his post on…
rallain | January 12, 2009I am not going to try and even surprise you with this. Notice the "tools:". This post is not about physics really, but something used in physics. When I get enough of these, I will put them together in a "tools" page - or you can just use the tools-tag.
Suppose you have some data. You want to plot that data and turn it in with your lab report. Your instructor (me) told you to be sure and include error bars on your graph.
What are error bars?
How do you add error bars - whatever they are?
Error bars are a way to graphically represent the uncertainty in a data point. Every time you take a…
rallain | January 12, 2009I am getting ready for classes. One class I am teaching is a physics course for elementary education majors. I really enjoy this class. There is hardly any math and the students learn by doing some experiments and then creating models. These models are then shared and discussed among the class. The basic points of the class are:
Help students learn the nature of science by doing sciency things.
Learn some science content by doing stuff (instead of listening to me talk about stuff)
Learn about how to teach science in elementary schools.
Explore the nature of learning.
I didn't really make…
rallain | January 10, 2009So, here is a video (from break.com - so you know it is likely fake).
null - Watch more free videos
If for some reason, you can not view this video, here is the plot.
Guy wears parachute and brings a portable thing like a see-saw.
Guy approaches large crane dropping a large mass repeatedly (I assume to flatten a dirt road)
Guy sneaks up an puts the see-saw under the area that the mass drops on and then stands on the other end of the see-saw.
Mass drops, guy shoots up and parachutes down.
So, why is it fake? I think the best thing is to give an analysis of the see-saw. To start this analysis…
rallain | January 8, 2009Here is an article from Wired.com that talks about a used cooking oil generator. It's a really neat idea in that the oil is right there anyway. Here is my problem - from the article:
A new garage-engineered generator burns the waste oil from restaurants' deep fryers to generate electricity and hot water. Put 80 gallons of grease into the Vegawatt each week, and its creators promise it will generate about 5 kilowatts of power.
If you put 80 gallons of grease into the thing, that has a finite amount of energy. 5 kilowatts tells you the rate the energy is created. This would be like saying "…