20171128

Physics quiz question: increasing string tension

Physics 205A Quiz 6, fall semester 2017
Cuesta College, San Luis Obispo, CA

"Strings [44|365]"
Gala Medina
flic.kr/p/9hXzj1

A C3 piano string[*] has a linear mass density of 10.8 g/m, and is stretched with a tension of 747 N. Increasing the tension would __________ the speed of transverse waves along this string.
(A) decrease.
(B) not change.
(C) increase.
(D) (Not enough information is given.)

[*] A. Stulov, "Physical Modelling of the Piano String Scale," Applied Acoustics, vol. 69 (2008) pp. 977–984, cs.ioc.ee/~stulov/appl08.pdf.

Correct answer (highlight to unhide): (C)

The speed v of transverse waves along the piano string depends on the tension F and the linear mass density (mass per unit length) (m/L):

v = √(F/(m/L)).

Thus increasing the tension F in the piano string would increase the wave speed (but would also not affect the linear mass density).

Sections 70854, 70855
Exam code: quiz06Ho0k
(A) : 1 student
(B) : 12 students
(C) : 32 students
(D) : 0 students

Success level: 71%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.73

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