Writing in AP Physics

Writing in AP Physics is typically done to explain phenomena, predict results and explain results. Each of these should be evaluated using a 3 point system called CER. In class I use the rubric below to determine the quality of a well written response. I believe it is well aligned with the AP scoring guidelines, and is sometimes more thorough.

To give an example that all can understand, here is a level 2 response in all categories for the following prompt: What classification of animal is a platypus?

Response: A platypus is a mammal because the platypus produces milk to feed its young. Since all mammals produce milk to feed their young and no other classification of animal produces milk, a platypus must be a mammal

Claim: A platypus is a mammal.

Evidence: A platypus produces milk to feed its young.

Reasoning: All mammals produce milk to feed their young and no other classification of animal produces milk.

In a Physics application, the evidence must come either from given information or be direct results from an experiment. It can be a description of a graph, numerical values or observable behaviors. Reasoning often starts with stating a law or relationship that is applicable to the situation and fully connects the law or relationship to the evidence and claim.

To give an example for the prompt "What were the sources of error for this lab experiment?" given the following lab data:

Example Response: The use of a hand timer to collect time data is a source of significant random error. The times recorded varied by up to 0.17 s from the high and low (trial 2 &3). Using the % difference equation, %diff = (difference/average)*100 the variance is (0.56-0.39)/0.46 = 37% difference from between the upper end and lower end of the range. In addition, it should be noted that 2 of the points were recorded below the average, and only differed by 0.04s from each other, with one data point responsible for skewing the average from 0.41s to 0.46s.In the event that the single data point (trial 2) had some additional factor causing the greater time, it may not be considered valid data. Given the range of the variance and the possibility that one of the data points is an outlier, we have reduced confidence in our results, especially unless more trials can be performed.

Claim: Hand timers introduce error

Evidence: difference in values from max to minimum is 0.17 s & one point is much further away from others

Reasoning: equation shows that 0.17s is significant because it represents a 37% difference & one point being further away than others may indicate a trial that is invalid, reducing confidence in the average.