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## 08 May 2009

### BOUX day

Every baseball announcer has a catch phrase; similarly, every physics teacher has some personal or instructional quirk that identifies and (hopefully) endears him or her to the class.

My own catch phrase is “BOUX!” This comes from an old Dave Barry column, in which he describes the difference between New York Mets fans (who say “Boo! You stupid bum!”) and Montreal Expos fans (who say “Boux! Voux dumme bumme!”) Or something like that.

Throughout the year, I write “Boux!” on papers that demonstrate major fundamental errors. For example, saying that a box must move to the right because it experiences a net force to the right – Boux! Saying that the acceleration of a ball is zero at the peak of its flight because its velocity is zero – Boux!

On the last day of class, I open a blank page in Microsoft word with the word “Boux!” at the top. The class is encouraged to shout out mistakes they might make that would earn a “Boux!”. This exercise serves several purposes. It is cathartic, in that the class sees that EVERYONE, even the smartest student, has at one time or another earned a boux. Furthermore, as students begin to think about the three hour exam coming up on Monday, they remind themselves of mistakes that they can easily avoid. My hope is that if someone begins, say, to use conservation of kinetic energy in a collision problem, that person might stop himself, saying “oh, wait, Mr. Jacobs would sure say “Boux!” to that, ha ha.”

The whole exercise is generally lighthearted and fun… and it produces an interesting study guide. Here’s a list of the class’s “Boux!” list from last year. Enjoy! And good luck on Monday.

1. Adding electric fields without considering direction

2. Putting centripetal force on a FBD

3. Mg always points down, not at an angle

4. Acceleration does not equal zero at the top of a ball’s flight

5. Units (or numerical values) on variable problems; no units on a numerical problem.

7. Putting a sign on the charge when calculating electric field

8. Using a point charge equation when a field was produced by the Almighty Bob

9. Putting anything other than a force on a FBD

10. One rope = one tension (Jacobs Law of tensions)

11. Object distances are never negative

12. Assuming equilibrium for an Fnet problem when a is not zero

13. Mixing up sin and cos when breaking vectors into components

14. Putting both components and a force itself on a FBD

15. Leaving a free response problem completely blank

16. Saying F=ma when only FNET = ma

17. Setting a random voltage = IR

18. Assuming that if heat is added, temperature goes up

19. Assuming KE is conserved in a collision

20. Using left hand for a right hand rule

21. Drawing rays that refract through a mirror or that reflect off of a lens

22. Using kinematics when acceleration is not constant.

23. Fishing for equations

24. Putting acceleration anywhere but toward the center in circular motion

25. A normal force does NOT necessarily equal mg!

26. Putting Fn not perpendicular to the surface

27. Measuring an optics angle not from the normal
GCJ