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Analysis of Online Discussions

Analysis of Online Discussions. Gerd Kortemeyer, May 2006. Problem. A bug that has a mass m b =4g walks from the center to the edge of a disk that is freely turning at 32rpm. The disk has a mass of m d =11g. If the radius of the disk is R=29cm, what is the new rate of spinning in rpm?.

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Analysis of Online Discussions

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  1. Analysis of Online Discussions Gerd Kortemeyer, May 2006

  2. Problem • A bug that has a mass mb=4g walks from the center to the edge of a disk that is freely turning at 32rpm. The disk has a mass of md=11g. If the radius of the disk is R=29cm, what is the new rate of spinning in rpm?

  3. Solution • No external torque, angular momentum is conserved • Bug is small compared to disk, can be seen as point mass

  4. Student Discussion • Student A: What is that bug doing on a disk? Boo to physics. • Student B: OHH YEAH ok this should work it worked for me Moments of inertia that are important.... OK first the Inertia of the particle is mr^2 and of a disk is .5mr^2 OK and angular momentum is conserved IW=IWo W=2pi/T then do this .5(mass of disk)(radius)^2(2*pi/T original)+ (mass of bug) (radius of bug=0)^2= (.5(mass of disk)(radius)^2(2pi/T))+ (mass of bug)(radius of bug)^2(2*pi/T) and solve for T

  5. Student Discussion (continued) • Student C: What is T exactly? And do I have to do anything to it to get the final RPM? • Student B: ok so T is the period... and apparently it works for some and not others.... try to cancel out some of the things that are found on both sides of the equation to get a better equation that has less numbers in it • Student D:what did I do wrong? This is what I did. initial inertia x initial angular velocity = final inertia x final angular velocity. I=mr^2, angular velocity = w... so my I initial was (10g)(24 cm^2) and w=28 rpm. The number calculated was 161280 g *cm^2. Then I divided by final inertia to solve for the final angular speed. I found final Inertia by ( 10g +2g)(24 cm^2)=6912. I then found the new angular speed to be 23.3 rpm. This was wrong...what did I do incorrectly?

  6. Student Discussion (continued) […] • Student H: :sigh: Wow. So, many, little things, can go wrong in calculating this. Be careful. […] • None of the students commented on • Bug being point mass • Result being independent of radius • No unit conversions needed • Several wondered about the “radius of the bug” • Plug in numbers asap • Nobody just posted the symbolic answer • Lots of unnecessary pain

  7. Where Online Homework Fails • Online homework can give both students and faculty a false sense of security and accomplishment • Most students got this problem correct • … but at what cost? • … how much physics have they really learned? • This would not have remained undetected in hand-graded homework

  8. … At the Same Time: • If you want to know how students really go about solving problems, this is the ideal tool: • Every student has a different version, so the discussion is not just an exchange of answers • All discussions are automatically contextual • Students transcribe their own discussion - compare this to the cost of taping and transcribing verbal discussions • Discussions are genuine, since the students have a genuine interest in solving the problems in the way that they perceive to be the most efficient

  9. Possibilities for Qualitative Research • Analyze students’ understanding of a certain concept • Find student misconceptions • Identify certain problem solving strategies • Evaluate online resources

  10. Possibilities for Quantitative Research • Classify student discussion contributions • Types: • Emotional • Surface • Procedural • Conceptual • Features: • Unrelated • Solution-Oriented • Mathematical • Physics

  11. Classifying Discussions From Three Courses Discussions from three introductory physics courses:

  12. Quantitative Research: Classifying the Problems • Classifying the problems by question type • Multiple Choice (incl. Multiple Response) have the highest percentage of solution-oriented discussions (“that one is right”), and the least number of physics discussions. • Physics discussions highest in ranking and click-on-image problems • Problems with representation-translation (reading a graph, etc): slightly less procedural discussions, more negative emotional discussion (complaints)

  13. Influence of Degree of Difficulty • Harder than 0.6: more pain, no gain

  14. Do Good Students Discuss Better?

  15. Conclusion • A lot can be learned from online student discussions in LON-CAPA • Ideal setup for discourse analysis: • Direct exchange of answers impossible • Discussions in context • Immediately transcribed • Even if not for research, reading them can help with just-in-time teaching • At the very least, gives a “reality check”

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