analysis
rallain | May 24, 2010While I am still fresh on the Space Jump topic, let me take it to the extreme. Star Trek extreme.
SPOILER ALERT
But really, is this a spoiler alert if it is from the trailer of a movie that has been out forever? Of course, I talking about the latest Star Trek movie where three guys jump out of a shuttle and into the atmosphere.
So, in light of the Red Bull Stratos jump, how would this jump compare? First, my assumptions:
This Star Trek jump is on the planet Vulcan. I am going to assume this is just like Earth in terms of gravity and density of air.
The jumpers in Star Trek have on stuff…
rallain | May 19, 2010A new video from the Red Bull Stratos Jump guys came out. Here it is:
This reminds me of an unanswered question about the Stratos jump that I didn't address on my last post on this topic. Commenter Long Drop asked about how much Felix would heat up as he falls from 120,000 feet. This is a great question. The first, off the bat answer is that he won't heat up too much. Why do I say this? Well, when Joe Kittinger jumped from over 100,000 feet and didn't melt. Still, this is a great thing to calculate.
How do you calculate something like this? I will look at this in terms of energy. For…
rallain | May 16, 2010I 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…
rallain | May 15, 2010I was going to just leave the oil spill in the gulf topic alone. Not because it isn't important, obviously it is. Rather, I wasn't going to do anything because I didn't really have anything to add to the topic. After a couple of readers requested it, I think I do have something to add. How exactly do you estimate the amount of oil flowing into the gulf?
What do I have to start with? A video. Here is a video of the undersea oil leak.
Now, I am not the first to estimate the oil flow rate (NPR on Purdue Prof's estimation and here a commenter make a quick calculation). Like I said, I am…
rallain | May 12, 2010ScienceBlogs.com is running "Ask a Science Blogger". The basic idea is that you, the reader, get a chance to ask questions to us, the bloggers. You can either post a comment in the link above or send an email to .
I would like to go ahead and answer one of the questions already posted. nemski asks:
How big does the world appear to an insect?
I like this question because it can be answered at different levels. First, what do you mean by world? If you mean "the Earth", then the answer would be that the Earth essentially appears the same to an insect as it does to us humans (from a size…
rallain | May 3, 2010This video seems like it is getting popular, but maybe that is because it is so awesome.
Maybe it is just me, but I find this video very visually satisfying. I love the way they compare the different runners.
Anyway, there is some physics here. Commenter Ben sent me the link to this video (thanks!) with some great questions. Which of the runners has a greater kinetic energy? What about the power? These aren't too difficult to answer, but the first thing is to get the data. There are several options (including just using a stop watch). But no, that is not good enough for me. Instead, I…
rallain | April 28, 2010Normally, 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…
rallain | April 27, 2010There 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…
rallain | April 24, 2010Check 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…
rallain | April 16, 2010If 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…
rallain | April 2, 2010In this part of the world, we have oak trees. Technically they are called live oaks - but I don't get it. Of course they are alive. I was at a soccer game and this is the tree I always look at.
Look how far those limbs extend horizontally. That branch is about 12 meters long. Why is this amazing? Have you ever tried to hold an 8 foot 2 x 4 board horizontally by holding one end? Pretty tough. How about I calculate the forces needed to hold that branch in place? I will do a simple model and then maybe later I can make it more complicated. Suppose I replace that limb with one straight…
rallain | March 29, 2010Here 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…
rallain | March 23, 2010I 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…
rallain | March 23, 2010I 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…
rallain | March 19, 2010Let me be clear. I am not really an attacker. If someone wrote a report about ski jumping or something and misused the word "momentum", no big deal. However, if you have a show that claims to be about SCIENCE and you are obviously putting a lot of money into this show AND a whole bunch of people will see and think this is science - then you need to be a little careful. I think shows like ESPN's Sport Science are a good idea - you know, introduce some cool science ideas by using cool sports. This show just needs some help.
Yes, I know I make mistakes. I try to correct them when I become…
rallain | March 13, 2010The most basic explanation of Pi is that it is the ratio of the circumference to the diameter for a circle. That seems simple enough, but it turns out that Pi is an irrational number - so you can't just write it down. Oh, I know that you are an uber-geek and you could recite the first 80 digits of Pi. But the question is - how many digits are enough?
In this post, I am going to assume that we don't know the true value of Pi (which is essentially true). I can then use propagation of error techniques to see how dependent different calculations are on the value of Pi.
Super Brief Intro to…
rallain | March 8, 2010Hat tip to Frank for sending me a link to this video:
If you have never done a demo like this (without the motorcycle), you should. It really isn't too difficult. Here is a video of my version:
Inertial demo from Rhett Allain on Vimeo.
So, the question is: is the motorcycle thing real or fake?
First, let me talk about the key aspect of this demo. Why don't the glasses move? Well, they move - but just not very far. The demo is supposed to be an example of Newton's Second law, or you could say it is the momentum principle (which is what I will use). If a force is applied for a short time…
rallain | March 4, 2010Check out this thing.
That is where the guy (Jem Stansfield of BBC's Bang Goes the Theory) shows how he built this thing. Here is part 2 where he uses it to climb a building.
Here are some questions:
Why does it not matter how powerful the vacuum is?
How does a vacuum cleaner work anyway?
How does the vacuum cleaner work?
I know this is not HowStuffWorks.com, but I guess I should show some stuff. The cool thing about a vacuum cleaner (think shop vac so that I don't have to deal with the brushes) is that it is just one thing - a fan. The fan essentially moves air out of the vacuum part of…
rallain | February 23, 2010I 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…
rallain | February 22, 2010My 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…