本题目来源于试卷: Wave Behavior C.1 Simple Harmonic Motion，类别为 IB物理学
[单选题]
The bob on a conical p1,fbz neu, d6x 5qi lpigtj;(:endulum is rotated at *e 2u9 k0p krcle2tm+rconstant speed such that it describes a horizontal circle of diameter 15 cm. A lamp is placed so that the shadow of the bob projected on a screen describes simple harmonic motion. What is the displacement of the k et2e *9cr+ml02rkupshadow after the bob has traveled a total distance of $30π\,cm$?
A. $0\,cm$
B. $15\,cm$
C. $30\,cm$
D. $30π\,cm$
参考答案: A
本题详细解析:
Explanation: For a circle of diameter $d$, circumference is $πd$. Thus the cicrumference in this case is $15π$. In this instance the distance travelled by the bob is exactly equal to twice its circumference. The shadow, therefore, has travelled two complete oscillations and is at exactly the same point at which it started. The displacement, therefore, is zero.
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