projectile
rallain | August 13, 2010You know I have trouble letting stuff go, right? I am still thinking about these crazy long basketball shots. Here are some more thoughts.
Really, there are two things I am interested in. First, commenter Scott Post suggests that the drag coefficient might be around 0.25 instead of 0.5. I don't know. For the discussion before, it doesn't really matter. My point was to see a numerical model for a falling ball would be similar to the time and distance from the video. Changing the drag coefficient to 0.25 gives values that are still close to the video. So, I still think the video is real…
rallain | November 24, 2008This is an old video, but still interesting. In this video clip, Kobe Bryant jumps over a pool of snakes.
You are probably thinking what I thought when I see that - this doesn't look real. Really, it must be fake. Why would Kobe jump over a pool of snakes? Isn't that dangerous (even if there were no snakes in there he could hurt himself). Video analysis is needed. Is this fake or is it real?
Start with my favorite video analysis tool (tracker). Use this to get position time data.
Step 1: Get the movie. I used Mpeg Streamclip to get the movie in quicktime format from the flash video…
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 | 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 of a video that involved projectile motion and I don't want to go over all the stuff again and again.
Let me start with a generic, one-dimensional kinematic equation:
This relates the position (s), the velocity…
rallain | September 4, 2008One 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 look for? Then I figured it out. The sky IS falling. It is ALWAYS falling and it has always been falling.
What is the sky? I am assuming the sky is the air. I will treat the air as a gas of single particles (which it isn't, but that's ok). So, why does this sky (air) do what it does? If you…