Finals Week

Finals Week

It’s final week here. This means faculty are wondering around, hyped up on caffeine and glee that the semester is almost over while the giggle while writing exams and cry while grading them (okay, maybe that’s just me). Writing finals is almost a religious act. We all have our own personal philosophies on why finals should exist, how much they should be worth, and how to write them. There are places where finals are required and they are required to be cumulative. There are places where exams aren’t required at all. There are places where finals are at the students leisure (I’ve heard that at Mt Hoyloke, students are on the honor system and can take their finals when they feel like it), and places where 4 finals can nail a student in 24 hours and no one really cares how much harder that makes it.

I have to admit, I see finals and standard exams as falling in the same bin. They are a one off exam that allows a student to convince the tester they can maintain concentration for 2 hours and cram a dangerous amount of information into their brain for just those 2 hours. Once upon a time I crammed enough information on biology into my brain to get just shy of perfect score on the Subject SAT bio test. That information is pretty much all gone now, and I’m really not sure what I proved with that score other than that I have the ability to cram biology into my head. And tomorrow I expect many of my engineering students will cram a frightening amount of physics into their heads, and 15 years from now the majority of them while have forgotten all but the smallest scraps of that knowledge. I’m mostly okay with that. What I hope they will remember 15 years from now is that they once were able to do physics and can do it again if they just stick their mind to it. And I’m hoping that they will remember that physics isn’t just pulled out of the air, but rather comes from study and experiment, and it comes from measurement and mathematics. I want them to understand that in their day to day lives, most experiences can be broken down to Work, Energy, Force and Torque, and many situations that look surprisingly different are utterly identical.

But how do I test this understanding on an exam?

I don’t know entirely. The best I can do is test their ability to recognize old questions in new words. While I don’t do this with all my classes, in some classes I will draw questions exactly from old test, but change the wording in such radical ways that it is almost impossible to see they are the same.

For instance, here are two problems I opted not to use:

1) A 0.8 m long sign extends from a wall supported by a rope as shown to the sign and a rope connected to the pole. If the sign has uniform density, what is the minimum coefficient of friction between the sign and the wall? (picture shows a sign on a pole with a rope connecting the sign to the wall at a 30 degree angle 0.2 m from a wall)

2) A very silly, very skinny monkey is hanging from a loop on the zoo wall as shown and is happily staring at a crowd of people. Assume the monkey’s weight is evenly distributed over his 0.8 m height. What is the coefficient of friction between the monkey’s foot and the wall? (picture shows a monkey configured like the sign, using one bent leg as pole and one straight leg as rope, and a 30 degree angle).

I opted not to use this problem mostly because it is hard to solve and the amount of time the students have for their final is actually shorter than the amount of time they have on regular exams. Otherwise, I like this type of problem mutation because it 1) is easy for students who bother to study past exams and can recognize patterns between problems, 2) requires the students to generalize between physical and biological systems, and 3) it’s just silly.

Tomorrow night I’ll be grading their exams and I’m not sure how much blogging I’ll get to due. I’m going to try to get a couple more posts in this week. Starting Monday, things should be much easier for a while (no more classes, no more books, no more students dirty looks… 🙂 )

EDIT: Click to get the sign version of the problem mentioned above. picture-1.png


  1. michael cassidy
    Dec 11, 2007

    Geeez you didn’t give us the diagrams!?

  2. Chris C
    Dec 11, 2007

    Would you care to teach at my school? It’s online! You can grade papers in your… well nevermind.

  3. michael cassidy
    Dec 11, 2007

    what’s and where online?

  4. Freiddie
    Dec 12, 2007

    Please can I see a diagram? And could you please tell me how to solve it?

  5. Hakan
    Dec 12, 2007

    Assuming the simplest case where the wall is straight and the pole is perpendicular, it’s an extremely easy problem to solve. Even the variants where the pole is not perpendicular but at an angle, it’s still too easy. If only my physics 105/106 questions were this easy.

    | \
    | \ rope
    | \
    | \
    | \
    |——- pole

    Does ASCII graphics still work for internet?

    Or maybe it’s because I did loads of ME 205 statics examples and exams. 🙂

    Disclaimer: I trained as an Mechanical Engineer, got my Bachelors, started my Masters and got bored with it and I’m working for IT for 8 years now. The hardest physics question I solve is where to put the telescope 🙂

  6. Freiddie
    Dec 13, 2007

    So *that*’s how it looks like! OK, makes more sense now.

  7. Freiddie
    Dec 20, 2007

    Is the answer sqrt(3)/6? Or is it sqrt(3)/2? Am I even close? If not, I’ll be groveling for a solution.

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