20191008

Astronomy midterm question: 15 hour sunrise to moonrise work shift

Astronomy 210 Midterm 1, fall semester 2019
Cuesta College, San Luis Obispo, CA

While giving a tour to visitors, a family member recounted how her father worked on their tree farm[*]:
[Dorothy "Dot"] Lombard said her father worked several years on the tree farm before he bought the property in 1956. He loaded logs into his four-wheel drive skidder, cut away brush and took lengthy notes. He would work from sunrise to moonrise.
Discuss what phase the moon would have when rising to signal the end of an approximately 15 hour work shift that began at sunrise. Support your answer using a diagram showing the positions of the sun, moon, Earth, and an observer on Earth.

[*] Zack Peterson, "'This Is a Great Forest': German Contingent Travels to Reading, VT, to Tour Model Tree Farm," Valley News (June 23, 2013), vnews.com/Archives/2013/06/GermanForesters-zp-vn-062213.

Solution and grading rubric:
  • p:
    Correct. Complete diagram (with the sun, moon, and observer on Earth), and discusses:
    1. assuming sunrise at 6 AM, then end of a 15 hour work shift would be at 9 PM; and
    2. the moon that rises at 9 PM would be highest overhead six hours later, at 3 AM, corresponding to the waning gibbous moon.
  • r:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Diagram and/or explanation has minor errors. Understands that work shift would end at 9 PM, but subtracts six hours instead to find the moon phase that is setting at 9 PM instead of rising at 9 PM.
  • t:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram or discussion. Typically chooses waxing gibbous moon, which is directly overhead at 9 PM.
  • v:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to draw a moon phase diagram and apply rise/overhead/set times.
  • x:
    Implementation/application of ideas, but credit given for effort rather than merit. Discussion not clearly based on a moon phase diagram.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Section 70158
Exam code: midterm01Sw3e
p: 20 students
r: 7 students
t: 8 students
v: 1 students
x: 0 students
y: 0 students
z: 0 students

Section 70160
Exam code: midterm01N0dL
p: 4 students
r: 2 students
t: 11 students
v: 4 students
x: 1 student
y: 1 student
z: 0 students

A sample "p" response (from student 4320):

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