Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 10.4
Michigan State University | College of Music
http://youtu.be/INfybEkRtgM
Discuss why the fundamental frequency of a bassoon (approximated as a closed-open pipe) is more sensitive to a change in air temperature than the fundamental frequency of a cello (a string fixed at both ends). Explain your reasoning using the properties of sound waves, string waves, temperatures, and standing waves.
Solution and grading rubric:
- p:
Correct. The standing wave frequencies for a bassoon will change, as the velocity of sound waves in air along the pipe depend on air temperature. The standing wave frequencies for the cello will not change, as the velocity of waves along the string do not depend on air temperature. - r:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. - t:
Nearly correct, but argument has conceptual errors, or is incomplete. At least recognizes the dependence of sound wave velocity on temperature. - v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Argument based on a factor of two difference between f1 = v/(4·L) and f1 = v/(2·L) for closed-open pipes and a string fixed at both ends, instead of on the difference of the temperature dependence of v in either case. May also argue that the bassoon is affected more by changes in air temperature because it somehow involves a larger volume of air. - x:
Implementation/application of ideas, but credit given for effort rather than merit. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Grading distribution:
p: 4 students
r: 5 students
t: 13 students
v: 16 students
x: 0 students
y: 0 students
z: 0 students
A sample of a "p" response (from student 1129) is shown below:
No comments:
Post a Comment