Thoughts and musings of Peter Kupfer


  • Category Archives Physics
  • Using the Red Bull Stratos Space Jump in Physics Class…

    When I heard that a man, Felix Baumgartner, was going to jump from space I was intrigued at how I can use this in class. It is one of the unique teachable moments that comes each year that as a teacher you need to capitalize on. It is one reason I am grateful to work in a district that doesn’t have a lock step teaching mentality, so I can diverge when needed.

    In any event, I searched most of Sunday night for someone that had posted data of the fall and was unsuccessful, so I created some myself. I started with this video:

    And watched him fall. I noted that after about 20 seconds of falling the speeds were displayed on screen. The speeds updated at .5 HZ (2/second) and I plotted the data. The data is as complete as the video allowed and I hope Red Bull posts the rest of the data, including altitude, later. I typed into a program called Graph (which is a free ware program I highly recommend and can be downloaded here.) I also put it into an Excel file to share with others which you can find at the end of the post.

    In addition, one of my colleagues found on-line someone who had recorded all of the ascent data and we also put that into Excel and made a graph of the ascent.

    You can see that the velocity graph curves, which awesome because we so rarely have a chance to graph a real work changing acceleration, or the jerk. So, we then created a very simple worksheet to use in class today along with the video to spark a discussion. If I wanted to spend more time on this activity I could have had the kids collect the data, but that wasn’t something I wanted to invest time in today.

    Here is a copy of the worksheet if you wish to use it.

    Red Bull Space Jump Analysis Sheet

    Jump Worksheet (PDF)

    Jump Worksheet (ODT)

    Here also is a copy of the raw data if you want to work with it.

    Excel File - Red Bull Stratos Data

  • Angry Birds & Physics

    For a while I have been trying to think of ways to incorporate Rovio’s fantastic game Angry Birds into my physics class. On twitter today a tweet sent me to the Sweeny Math blog to a post about using Geogebra to analyze Angry Birds. In short Mr. Sweeny had his students analyze the trajectory of an Angry Birds launch (I think he must have done a screen shot post launch) and then let Geogebra find the curve fit of the line. Now, I have been working Geogebra this year and really find that it is a powerful program for analyzing mathematical systems, but I don’t know that it is best tool for analyzing an Angry Birds video.

    For analyzing video in class (and for fun) we use a freeware program called Tracker. Tracker is a pretty amazing program especially considering software of this quality can cost a lot of money and still not be as good as Tracker is. I didn’t really have a project in mind, so I decided to jump into this analysis as an open-ended question which are becoming all the rage in science classes. So, I went to YouTube to download an Angry Birds video. (I downloaded the video using Easy YouTube Video Downloader which is a FireFox Add-On.)

    The basic premise of Tracker is that you click on a spot of an object for every frame of a video and Tracker than turns the grid of the video into an x-y coordinate plane and can compute the displacement and velocity of an object. Here is how the Tracker screen looked after I finished clicking:

    Angry Birds Image with Tracks

    So, now I wanted to get some data. This is where Tracker is awesome.

    Angry Birds Launch xvt & yvt

    Angry Birds Launch Vx v t & Vy v t

    So, these graphs show the shapes and relationships that we would expect from a projectile launch: Constant velocity in the x-direction and acceleration in the y-direction. However, now, I wanted to do some analysis of the accuracy of the program. So, from here I was going to treat this first video as a control and assume that it was correct. In order for Tracker to return numerical data the scale of the video has to be set so that the program knows how “large” each pixel should be.

    I tried to find an object in the video that would always be the same and so I settled on one of the yellow birds. I adjusted the size of the bird until the slope of the Vy v. t graph was -9.81 which should the acceleration of gravity.

    Angry Birds -- Define the Schale with the Yellow Bird Angry Birds - Vy v t Graph for Yellow Bird

    In order to test if other objects on the screen would follow the same behavior, I tracked the motion of one of the falling pigs.

    Angry Birds -- Falling Big Angry Birds -- Vy v t -- Falling Pig

    So, the acceleration of the pig was the same as the yellow bird, so it seems to work out.

    From here I’m not sure where I would go next, one problem I can see is that depending on the zoom of the level I don’t know if I could use the same size of the yellow bird consistently between videos. I think if I could zoom in the closest level in each video in the game then I could use the yellow bird size across videos. After writing this post, I found that A Professor of Physics at Southeastern Louisiana University tackled this same issue and came to similar conclusions, but didn’t really provide any revelations into the issue of zooming in on the bird. He did remind me Tracker’s ability to track motion of a panning video, which may help since all of the Rovio videos on YouTube start with the default zoom. He did try to include a little more quantitative analysis in his second Angry Bird’s analysis, but made the assumptions as before. (In case you haven’t seen enough, here is a similar analysis of Super Mario Brothers.)

    The next experiment I want to try is to determine the mass of the birds. This video wouldn’t work well for it, but if you could assume the density of the rock barriers and then find the volume (find the height and width using the scale and the assume the depth) then you could find the mass of the rock barriers and using the conservation of momentum you could find the mass of the bird. I am sure there are other ways to go, but that would be a fun start.

    Here is the final result:

  • Impulse Momentum Theorem Demonstration Question

    We were trying work out the impulse-momentum theorem by dropping an object onto the force plate from the same height so they would have same initial velocity and momentum. In theory we wanted to them to fall on the plate and stick so that pf would be zero. We have several remaining questions, but the most confusing part for were bumps in the data after the impact. If you were find the entire area as if to say that Ft = Delta p which would you find the area of?

    Force versus time graph for a impulse momentum lab

  • Gravity, Not Just a Good Idea, but the Law! (of Physics!!)

    So, here we have two different groups who think the laws of the physics don’t apply to them.

    First, the Bose Wave Radio people have a radio spot that claims that the sound from the Bose is so good, it defies the laws of physics. If think the absurdity of that statement is self-evident, so I will just leave it at that. I can not find the radio clip, but here is a copy of the review.

    Second, we have a woman in Joliet who seems to have forgotten that gas particles expand as the evaporate. Here is a summary I wrote for my submission to the Darwin Awards:

    It appears that a 27-year old Joliet woman is quite evolutionary challenged, but she continues on. At some point on the night of August 27th, the woman in question decided to travel to the gas station to fill her can. While at the gas station, our herione didn't want to put the gas can on the ground, so as to ground all of the pesky electrons. Rather she left it on the plush seats in her car in the hopes that the friction between the plastic and the upholstery would kick up some extra electrons that might help her get some light to see whether or not her can was full. Well, that plan backfired, and she was not getting the light she needed. Fortunately she found her pocket ligther and checked the inside of the can. Well, this ignited the whole thing on fire. Now, realizing that this may be an concern, the young woman pushed her can 5 feet in order to keep the pump from blowing up while her car was destroyed thus ensuring her potential to breed. If asked afterwards, one could only assume she would say that she saw gas in the can. Submitted on 08/29/2009 Submitted by: Peter Kupfer

    Slush Pile: For Want of a CFL via kwout

    Again, I am really not sure if I can add any more to this story, but the phrase, “You can’t make this stuff up,” comes to mind.  Seriously, why would someone do this? It just boggles the mind.

    The bottom line here folks is, don’t mess with physics. With a knowledge of physics you can control the world. Now a fun video from my two favorite physicists.

  • Illinois Keeps Making it Easy to be Mocked…

    The headline of this article caught my eye first. Pluto a Planet Again — On Friday the 13th, in Illinois, but the title is a little over zealous. Apparently we are just honoring the founder of Pluto, but still I wouldn’t put it past the State of Illinois to embarass itself in this way.

  • Pluto is Dead

    The international community (at least some of them) have declared that Pluto is no longer a planet, rather it is a dwarf planet. I think this is an extremely cool event. I always wanted to know who makes those kinds of decisions and who has that authority, now we know. Ultimately I guess the new definition will only stick as long as people accept it. This has got to be a big boom for the text book industry too, because now they have to re-write (and re-sell of course) text books to account for this change.

    Personally, I think it is a good decision. Where does Pluto get off thinking it is a planet. It is a little chunk of rock, smaller than our moon (I beleive) that doesn’t even bother staying in the same plane as the rest of the planets. Unbelievable!

    I am happy with 8 planets. I think it is a good move. I am anxious to see how the rest of the world accepts this.