A deviation in scoring protocol?

[justdoitdt]

I'm looking at the AP Mech C practice FRQ:

https://apclassroom.collegeboard.org/29/question_bank/create/preview/item/1320757

 

On part c, the scoring rubric says "1 point is earned for [graphing] a pair of quantities that could be used to determine g - students must graph measured, not calculated quantities."

 

Does this mean that graphing k∆x vs. Msinθ would not earn the point? If so, that would deviate from past AP Exams, would it not?

[justdoitdt]

A very interesting question, OP. Color me flummoxed.

[FizziksGuy]

Graphing the empirical k_delta_x vs. Msintheta would work, but not the theoretical.  They want you to determine an empirical value for g, not do a mathematical exercise that results in a 1=1 proof.

[justdoitdt]

Graphing k∆x vs. Msinθ would result in a slope of g. Not a slope of 1. But since k must have been calculated, the wording of the rubric makes it sound like this solution wouldn't count.

[FizziksGuy]

Right, but it's ultimately a proof of 1 vs. 1, not an empirical derivation of g.  You're proving something is itself if you use theoretical values.

[justdoitdt]

I'm not following you, Fizziks. None of the graphed values (k∆x vs. Msinθ) are theoretical.

• k - must be calculated somehow, based on measurements of force, displacement, and/or the like
• ∆x - measured
• M - measured
• θ - measured
• sinθ - calculated

What theoretical values are you referring to?