centripetal
rallain | April 6, 2009Cats can be entertaining - especially when they are someone else's cat and that someone made a video. Really, this post is about analyzing video with Logger Pro (in a tutorial type fashion). I just happens that I chose this cat video to analyze. Here is the video:
I am going to look at the part where the cat gets on the fan. I will try to step through the analysis so you can do your own.
Get the video
Actually, the first step is to find a video. YouTube has tons of stuff. Also, you could make your own video with a camera. A couple of things to make your life easier:
A non-zoom video.…
rallain | March 31, 2009What is a fake force? A fake force is one of those forces that introductory texts tell you aren't real - like centrifugal force. They aren't real in the sense that they are due to one of the fundamental interactions. Basically, introductory texts (and even blogs like this one - not a bad summary of real vs. fake forces) attack the centrifugal force. This is because it is so common for students to want to use these faux forces in the wrong way. Better to just not use them at all.
Anyway, there are times when faux forces are awesome. Just to be clear, a faux force is needed to use normal…
rallain | March 17, 2009Dear Ruff Ruffman,
My kids really like your show. However, there is a problem. You promote it like it is science, but the content keeps having mistakes in it. Previously, I pointed out your mistake about in infrared thermometer (if can't remember, you said the thermometer measures the temperature with a laser. In fact, the laser is just used to aim.)
So, you see, I don't just like to randomly attack people. The problem is that you are saying "hey look at science" but your science is wrong. I suggest you either a) stop pretending to be a science show or b) get a science advisor (I am…
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 | October 7, 2008In this post, I am going to talk about real and not real forces as well as the fake centrifugal force (if you don't like the word "fake" you could replace that with "fictitious")
First, an example: suppose you are in a car at rest and press the gas pedal all the way down causing the car to accelerate. What does this feel like? If I weren't skilled in the art of physics, I might draw a diagram something like this:
Yes, maybe someone would add gravity and the chair pushing up, but this shows the…
esiegel | January 28, 2008One of the worst teaching tools physicists use (and they almost all do it) is to tell students,
There's no such thing as centrifugal force.
What can you do when the top physics education website says, "It is important to note that the centrifugal force does not actually exist. We feel it, because we are in a non-inertial coordinate system." There's a very funny comic over at xkcd that goes as follows:
Well, what's the deal? What really goes on, physically, and what causes a centrifuge to work? Is your physics teacher right, or is there more to the story than "the centrifugal force does not…