Physics 205A Quiz 6, fall semester 2017
Cuesta College, San Luis Obispo, CA
A "seconds pendulum" is defined to be a pendulum with a period of exactly two seconds[*]. The length of string used to construct this pendulum at the equator was measured to be 0.99065 m during an expedition in 1735[**]. Based on this result, the magnitude of the acceleration due to gravity g at the equator in 1735 was:
(A) 9.6859 m/s2.
(B) 9.7773 m/s2.
(C) 9.8696 m/s2.
(D) 9.9628 m/s2.
[*] wki.pe/Seconds_pendulum.
[**] Michael R. Matthews, Time for Science Education: How Teaching the History and Philosophy of Pendulum Motion Can Contribute to Science Literacy, Springer Science & Business Media (2000), p. 147.
Correct answer (highlight to unhide): (B)
The period of a pendulum is given by:
T = 2·π·√(L/g),
Since the period T = 2 s and string length L = 0.99065 m are known, the acceleration due to gravity g can then be solved for:
g = L·((2·π)/T)2,
g = (0.99065 m)·((2·π)/(2 s)/)2 = 9.7773235999 m/s2,
or to five significant figures, the acceleration due to gravity is 9.7773 m/s2.
(Response (A) is (π·L)2; response (C) is π2); response (D) is π2/L.)
Sections 70854, 70855
Exam code: quiz06Ho0k
(A) : 1 student
(B) : 34 students
(C) : 7 students
(D) : 3 students
Success level: 76%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.82
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