Unformatted text preview: Rubric for Quiz 5B, Physics 7A
A/B Winter 2011: (Points indicated at the end of the category descriptions) 1a) 20% Q : Volume is decreasing => work is positive => energy is entering the system, or work is done on the system by the surrounds…10 points T: Volume is decreasing => work is positive, but stated that pressure is constant in the process…8.5 points W: Volume is decreasing => work is positive, => work is entering the system…(wording not quite right— heat enters or leaves the system but work is done on or by the system) 9.5 points Y: Work is positive; but incomplete, wrong, or no reasoning given…6.8 points E : Work is negative, or zero…4 points R : No response…0 points b) 20% Q : Use Ideal Gas Law: Tf = (PfVf)/(nR), with correct numbers and units plugged in…10 points W : Correct formula but with numerical error/ wrong units…9 points Y: Calculated initial instead of final temperature…8 points E : Incorrect application of Ideal Gas Law: Like ΔT = (PΔV)/(nR)…7 points R : Using a wrong concept like ΔEth to calculate Tf …4 points T : No response…0 points c) 20% Q : Used ΔEth = (5/2)nRΔT = (5/2)Δ(PV), and obtained correct numerical answer…10 points W : Minor error, like using kB instead of R…9 points T: Some progress along the right track…7.8 points E : Using ΔEth = Q+W and finding W = area of rectangle…6.7 points Y: Using an incorrect equation such as: ΔEth = (5/2)nRTf…6 points R : Stating the formula for ΔEth and maybe writing an answer, but no work or explanation given; or an incorrect application of ΔEth = (5/2)nRΔT, for example, using Q = ΔT…4 points Z : No response…0 points d) 20% Q : ΔU = ΔEth + ΔEbond = ΔEth, because there is no phase change so ΔEbond is zero. Even if the numerical answer to c) is wrong, you get full credit for this part if your reasoning is correct (you don’t get penalized twice)…10 points A: Correct answer with reasoning, but missing Δ’s in one or more terms of ΔU = ΔEth + ΔEbond = ΔEth, for example, stating that Ebond = 0…9.5 points T: Correct answer with incorrect or no reasoning…8.5 points W : ΔU = ΔEth + ΔEbond = ΔEth, wrong or no numerical answer, but correct justification…8.5 points Y: ΔU = ΔEth, ΔEbond = 0, no or wrong numerical answer, and no reasoning…6.5 points E: Used some related equation like ΔU =(5/2)nRT, or ΔU = Q+W and using given Q, and W = b*h…5 points R: Incorrect response…3 points Z: No response... 0 points e) 20% Q: Used W = ΔU – Q, plugged in answer from d) and the given Q to get W, and got a negative W as expected. Even if the numerical answer to d) was incorrect, you get full credit (you don’t get penalized twice)…10 points W: Correct idea, but numerical errors, but correct sign for W…9 points Y: Wrong sign for W (
instead of +)…6 points E: W = area of the rectangle , or stated that the areas curved parts cancelled out, so W = base*height…7 points R: Not much progress, stated W =
Integral of (PdV) or W = Q+W…4 points A: Incorrect response, such as areas under curve cancel out so W = 0…4 points T: No response…0 points ...
View
Full Document
 Winter '08
 PARDINI
 Energy, Work, points00

Click to edit the document details