acceleration

Crazy, but I was on CNN Saturday night. They contacted me at the last minute to talk about the Red Bull Stratos Jump. Here is a screen shot to show that I am not making this up (or that I have awesome photoshop skillz). Looking back, maybe I looked like an idiot. Really though, it wasn't my fault. I thought we were going to talk about physics. The first two questions threw me for a loop. Here are the two questions and my response (roughly paraphrased): Will Felix survive the jump? Answer: I guess so. Is there a scientific reason for this jump? Answer: I thought we were going to talk…
And there's parliament. Ok - sorry, I had to make a "Tom (Swans on Tea)" title for this one. Tom, forgive me. Here are two great circular motion videos. First, this one is from Dale Basler. He made himself a fine little floater-type accelerometer. Better than just make it, he made a video of the accelerometer in his car going around a round about. Check it out. Bobber Meets Roundabout from Dale Basler on Vimeo. So, if he is driving at a constant 10 mph, how big is the round about (traffic circle)? Next video - more silly kids First, I saw this one on ZapperZ's Physics and Physicists who…
I am excited. This Wednesday, the MythBusters are doing the giant water slide jump. Maybe you are new to the internet and you haven't seen this video. Here it is: And since it is as old as the hills, of course I have already analyzed it - actually twice. First, the video is fake - but it is an excellent fake. Here is another site with details on how this was created. What did I look at in my previous posts? Here is a summary. The video is difficult to analyze because of perspective changes. Even with these problems, nothing says it has to be fake. The vertical acceleration during the…
I was going to make this as a video tutorial, but it just didn't work out right. So, here it is in blog post form. How do you deal with a video that zoom and pans at the same time? You could keep on adjusting the coordinate axis AND adjust the scale for each frame - but sometimes that is not possible. Tracker Video has a great tool to handle these types of videos - the calibration point pair. The basic idea is that you identify two points in a scene that should be stationary (part of the background) and track those two points. Tracker will then adjust the coordinates and scale to make…
Normally, it isn't really news when a show doesn't do anything wrong. I am making an exception for ESPN's Sport Science. Here is part 2 of Sport Science trying to reproduce Kobe Bryant's "jumping over a car" stunt. And here is part 1 (although part 2 is the only interesting part). See. I can get along with Sport Science. Anyway, I am not sure that Kobe's jump used wires - but I assumed it was fake. Here is my analysis of Kobe's Jump (this stuff is old). And this is the plot I created from video analysis of Kobe. The tough thing about looking at Kobe's jump is that he changes his body…
You see in my experimental determination of the location of the accelerometer in an iPod, I used two different iPhone apps. Let me briefly mention some of the free iPhone apps that give you acceleration data. AccelGraph: This is one of the apps I actually used. What do I like about it? Well, it can record x, y, and z acceleration data and then you can email it to yourself. What could make it better? How about a timed start to record (like start recording in t seconds) and a preset record time. This would allow you to set up your experiment and get your iPod set up before you start. As…
There are several free iPhone-iPod Touch apps that let you look at the acceleration of the device using the built in accelerometer. I was planning on reviewing some of these free apps, but I didn't. When I started playing around with them, it was clear that I needed some way to make a constant acceleration. There are two simple ways to do this - drop it, or spin it in a circle. I decided to go with the circular motion option because I like my iPod and because Steve Jobs told me to. While playing with this, I realized that the acceleration depends on the distance of the sensor from the…
Check this out. So, the guy jumps from 150 feet into some cardboard boxes. Why are the boxes important? You want something that can stop you in the largest distance to make your acceleration the smallest. Here is my Dangerous Jumping Calculator. Basically, you put in how high you will jump from and how much distance you will take to land and it tells you your acceleration. You will probably need this G-force tolerance info from wikipedia. One problem - this calculator doesn't really work for this case. It doesn't take into account air resistance. Does air resistance even matter in this…
You probably already know how I feel about the "media" and their physics explanations (see attacks). Let me summarize the problem. There are a whole bunch of cool shows on tv that deal with sciency stuff - that is good. These shows then try to teach some science along with their demos and explosions and stuff. This is also good. However, they usually butcher the explanation part. Some of them (ESPN's Sport Science) must just literally make stuff up that sounds cool. I understand that in common usage, things like "force" can be used lots of different ways. I am ok with that. Also,…
If you have been on the internet, you surely have seen this website showing the sizes of different starships. Way cool. Here is a small sample - but it doesn't do the site justice. You really need to go browse around. Of course, I can't let something like this just go. One of the things I always think is interesting is to consider objects of different size. Perhaps the general idea is that you can just scale stuff up or down as you like. But, it doesn't work this way. Let me start with my own spaceship. It is a sphere with a thruster on the back. It just holds one person. Now, what…
Here is a quick Apolo Ohno quiz. Which one of these pictures is fake? If you picked picture B - you are probably correct. That is a picture of "Apolo" being catapulted into a pool of slime at the Nickelodeon awards show (click on the link to see the video - I don't think I can embed it). Ok - time to crank out an analysis. I think I could approach this analysis from a couple of directions. Since all I have is a crappy version of the video, I could just look at "could this be possible"? The other analysis I could do would be to measure his acceleration in free fall. Let me start with…
I already looked at ESPN's Sport Science episode where they calculate that Marshawn Lynch produces 54,000 watts when pulling some tires. Yes, that is way too high. However, what would happen if some was actually that powerful? What could that person do? How fast could they run 100 meters? That is what I am going to calculate. First, I am going to assume that Marshawn has a mass of about 100 kg. Also, let me say that he can produce 54,000 watts no matter what his speed. Take a short time interval. During this time, Marshawn will increase his speed from say v1 to v2 this would be a…
I happened to catch two parts of two different episodes of Meteorite Men - a show about two guys that look for meteorites. In both of the snippets I saw, they were talking about a debris field for a meteor that breaks up. In these fields, the larger chunks of the meteorite are further down in the field. Why is this? Let me approach this first from a terminal velocity view. This requires a model for air resistance. I will use the following: Where: rho is the density of air A is the cross sectional area of the object C is a drag coefficient that depends on the shape of the object v is the…
I had so much fun creating graphs for the Red Bull Stratos Space Jump calculation, that I figured I should make some more. Can you fall faster than terminal velocity? That is the question. Air Resistance Air resistance is a force exerted on an object as it moves through some stuff - air in this case. The magnitude is usually modeled as: Rho is the density of the stuff the object is moving through A is the cross sectional area of the object C is the drag coefficient of the object - this depends on the shape (a cone would be different than a flat disk) v is the magnitude of the velocity of…
My last Olympics post may have been a little complicated. I am going to try to make this one a little easier. In this post, I want to look at the landing portion of a ski jump. This could apply to THE ski jump, but there are some things in that even that make it a little more complicated (but I might come back to that in another post). For this case, I will consider the freestyle event - aerials. I didn't search too long, but here is a nice short video. First, a quick estimation of how high they are "falling" from on the way down. In that video, the jumper takes about 1.5 seconds to get…
Yesterday's post on a variation of the "Twin Paradox" with both twins accelerating was very successful-- 337 people voted in the first poll question, as of a little before 9am, and the comments to the original post are full of lively discussion. That's awesome. I wish I could take credit for it, but the problem posed is not original to me. It comes from a 1989 paper in the American Journal of Physics, which also includes the following illustration setting up the situation: The article contains a full explanation, and also the following figure illustrating the result: The correct answer is…
In a MythBusters episode some time ago, Adam and Jamie jumped off a building. There was some cool stuff in this, but I want to focus on the acceleration data they collected. Before jumping into a pit of foam, they first wanted to test the set up by dropping a dummy into it and measuring the accelerations. Lucky for me, they showed a quick screen shot of their data. Note: I previously posted the calculations for jumping and stopping off of a building. For me, I see this and think - numerical integration. Before that, let me look at the physics. Here is a diagram of someone jumping off a…
This is great. Many people have already reported google's apple-dropping homepage in honor Newton's birthday. In case it disappears, here is a screen shot. So, I got this awesome note from Dale Basler. He said that his class had analyzed this falling apple animation. What a very Dot Physics-y idea (check out his analysis). He said they were questioning the results which might be due screen capture issues. I decided to reproduce this. I captured the motion with Apple's Quicktime X screen recording feature. I then used Tracker Video Analysis - which now has an autotracking feature that…
One of my students showed me this game, Fantastic Contraption. The basic idea is to use a couple of different "machine" parts to build something that will move an object into a target area. Not a bad game. But what do I do when I look at a game? I think - hey! I wonder what kind of physics this "world" uses. This is very similar to my analysis of the game Line Rider except completely different. Fantastic Contraption gives the unique opportunity to build whatever you want. This is great for creating "experiments" in this world. The first step is to "measure" some stuff. The game…
Fight Science is an entertaining show. Great graphics. The basic idea is to look at the science in different fighting styles. They had a clip-style commercial on it during a MythBusters episode I was watching. And from that, I can say that the kicking looked cool, but the science needs some work. The Setup The basic idea is that they wanted to compare kicks from different fighting styles. From what I can gather, they collected data by having some dudes kick this "kicking bag". During the kick, they measured the force exerted on the bag and they had a sensor on the kicker's leg - I…