analysis
rallain | September 13, 2008There 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. These are used to keep track of how the origin is moving).
Below is the y position of the rider as a function of time:
In this situation, the rider falls about 100 meters. A quadratic line is fit to the data…
rallain | September 13, 2008Scale 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).
The goal will be to put the linerider in a free fall (where air resistance should be able to be ignored) and determine his (it could be a she, it is difficult to tell) acceleration in LU/s2. Then we can determine the conversion factor from LU/s2 to…
rallain | September 6, 2008Here is the video in question:
Looks too incredible to be real for me. That is when I start to question things. Is this fake or not? To answer this, I took a clip that showed a person launching a grocery item over the isle. This was a good shot to look at because it was *mostly* perpendicular to the camera view. I then used [Tracker video analysis (free) tool](http://www.cabrillo.edu/~dbrown/tracker/) to get x-y-time data for the flying projectile grocery. The scale was difficult, so I just guessed that the guy on the left was 5 foot 10 inches. Here is the vertical position data for…
rallain | August 28, 2008I 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 before. Would it work?
First, how do things get in orbit? Orbit is a motion in which the gravitational force on an object makes it move in a circle around another object. In order to be in a circular orbit, it takes a certain amount of energy.
Let me just start with some calculations. How fast…
grrlscientist | August 3, 2008Okay, here's something totally weird: I ran across a site that analyzes your browser history and uses a mathematical algorithm to identify your gender. According to this algorithm, I am male;
Likelihood of you being FEMALE is 6%
Likelihood of you being MALE is 94%
Hrm. Do you suppose this is the reason my email boxes are all jammed with ads to increase my penis size? How about you? Does your browser history predict that you are male or female?
dmunger | August 6, 2007It would be difficult to come up with a more frequently confused concept in psychology than reinforcement and punishment. In fact, "reinforcement" and "punishment" aren't difficult to understand on their own: Reinforcement simply means any means of increasing or encouraging the designated behavior; punishment is any means of inhibiting or decreasing the designated behavior.
It was only when B.F. Skinner devised the "positive" and "negative" descriptors that he became the bane of college students for generations to come. Rather than "positive" and "negative," things would have been much…
dmunger | June 20, 2007Euro-update 4: Sperm whale perception
Tuscany is about the last place you might think to go to speculate about the visual system of a whale, but when you're spending three weeks relaxing in a secluded villa, you have a lot of reading time. I've been reading Moby-Dick.
Herman Melville describes the sperm whale with almost obsessive detail in the book, from the shape of its tail to the nature of its skin.
In one chapter, devoted to contrasting the head of the right whale and the sperm whale, we find amazing speculation about both the human and sperm whale visual system. Remember, this was…
dmunger | April 26, 2007When Shelley Batts wrote up a report on an article about antioxidants in fruits, she never expected to get contacted by the copyright police, but that's exactly what happened. She had reproduced a table and a figure from the article, and got this notice from an editorial assistant at the publisher:
The above article contains copyrighted material in the form of a table and graphs taken from a recently published paper in the Journal of the Science of Food and Agriculture. If these figures are not removed immediately, lawyers from John Wiley & Sons will contact you with further action.
She…
dmunger | April 17, 2007Earlier today I wrote a post about optical illusions. I was hoping it would distract me from thinking about the Virginia Tech shootings. It didn't. I began to see connections between the illusions and the tragedy: That sinking feeling that somebody was being shot, that spiral like a gun sight.
The problem is that human brains are connecting machines: we can connect anything to anything else. Trying not to think about the shootings was the worst thing I could do. How should I be handling it? I should be talking about it directly -- preferably face-to-face or over the phone. I did spend some…
dmunger | January 18, 2007Last week's post on how sound affects perception of visual events was the most popular post ever on Cognitive Daily, with over 15,000 visits. This was thanks to links from both Fark's technology page and digg.com. Yet commenters on both sites expressed disappointment with the demo. I wasn't especially happy with it either, but then again, I didn't realize that more people would look at that one post than visited the site in all of February last year!
The problem with the movie is that it's showing two conflicting phenomena. Turn your sound down and watch the movie:
Even though the motion of…
dmunger | October 24, 2006There was plenty of interest in yesterday's audio-visual illusion. In case you missed it, I'll post it again here:
Play the movie with the sound turned up. If the illusion works, then you'll see a dot flash twice, accompanied by two beeps. But actually the dot only flashes once. Unfortunately, we've had a hard time getting viewers to see the illusion (as of this writing, just over a quarter of those viewing the video claim to see two or more flashes). I have a couple ideas about why people don't seem to see it reliably here on Cognitive Daily, and I'm going to investigate them further on…