Analysis of Online Discussions Gerd Kortemeyer May 2006

Analysis of Online Discussions Gerd Kortemeyer, May 2006

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

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

Student Discussion o o 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. 5 mr^2 OK and angular momentum is conserved IW=IWo W=2 pi/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(2 pi/T))+ (mass of bug)(radius of bug)^2(2*pi/T) and solve for T

Student Discussion (continued) o o o 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 (10 g)(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 ( 10 g +2 g)(24 cm^2)=6912. I then found the new angular speed to be 23. 3 rpm. This was wrong. . . what did I do incorrectly?

Student Discussion (continued) […] o Student H: : sigh: Wow. So, many, little things, can go wrong in calculating this. Be careful. […] o None of the students commented on n n n o 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

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

… At the Same Time: o If you want to know how students really go about solving problems, this is the ideal tool: n n 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

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

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

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

Quantitative Research: Classifying the Problems o o 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 clickon-image problems Problems with representation-translation (reading a graph, etc): slightly less procedural discussions, more negative emotional discussion (complaints)

Influence of Degree of Difficulty o Harder than 0. 6: more pain, no gain

Do Good Students Discuss Better?

Conclusion o o A lot can be learned from online student discussions in LON-CAPA Ideal setup for discourse analysis: n n n o o 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”