# A deviation in scoring protocol?

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

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 kx vs. Msinθ would not earn the point? If so, that would deviate from past AP Exams, would it not?
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A very interesting question, OP. Color me flummoxed.

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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.

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Graphing kx 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.

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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.

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I'm not following you, Fizziks. None of the graphed values (kx 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?

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