The Top 6 mistakes people make on the IB SL Physics Test

Okay, so with the IB SL Physics and AP Physics B tests coming up fast (yikes!), there are 6 things that most IB SL Physics kids screw up on when they are taking the test. These are six things that you WON'T screw up on, because you'll know to watch out for them!


1. Unit Conversions: This may seem obvious, but the test is timed- its easy to forget to convert wavelengths of light (for example) to meters before plugging them into the v = fλ equation. Remember to read the question and make sure that the units are right BEFORE you start calculating! 


Use your brain! If you're converting a big unit to a small unit (ex. meters to centimeters), simply raise the number to a POSITIVE power (because there are more centimeters in a meter than meters in a centimeter). If you're converting a small unit to a big one (ex nanometers to meters), raise the number to a NEGATIVE power (same reason as above, I'm just too lazy to type it out ;))


2. Radians/Degrees: ESPECIALLY for AP Calculus students! Remember to set your calculator mode to DEGREES before you start. Also, remember that the formula Θ = λ/b gives you an answer in radians, not degrees!


3. Explanations: Remember, even if your answer makes sense, you can only get points if you explicitly cite a physics law, principle, or equation!

4. Mass of an electron/proton & elementary charge: A lot of people stare at problems like this: 

"A proton moves in a circular path perpendicular to a 1.14 T magnetic field. The radius of its path is 8.00 mm. Calculate the energy of the proton." 

and say "wait, what? I don't have enough information! I can't solve this!" 

You get a MASSIVE list of constants in the IB data packet (the yellow one). USE IT! The gravitational constant, elementary charge, coulomb constant, and masses of protons, neutrons, and electrons are all in there. You also get conversion constants for kg->amu->MeVc^-2

(really helpful!)

5. Definitions: Look at the number of points on a question. If the maximum number of points is 2, try to write 3 things- cover all your bases, so if you get something wrong, you can still get some points. Remember, definitions are graded on the number of points you hit.

6. Trying to memorize formulas (and doing it wrong :P): How do I know that this can screw you up (ToK moment?)? Personal experience... I memorized the fv = λ formula backward ( fv = λ) and it messed me up for weeks... Its like trying to memorize a piece of music- if you memorize it wrong, nothing can help you, and you'll mess up even with the music right in front of you. Either DON'T try to memorize the formulas (my advice) or if you choose to do so, make sure you do it right!

Good luck! And may we beseech the blessing of almighty test graders upon this great and noble undertaking.

--

Satya