本题目来源于试卷: Wave Behavior C.5 Doppler Effect，类别为 IB物理学
[单选题]
A car and a bicycle move in the same direction with speeds of $v_0$ and $v$ respectively as shown in the diagram below.
The car driver uses the horn to warn the cyclist. The frequencies of the sound heard by the car driver and cyclist are $f_o$ and $f$ respectively. Which of the following can be correct when $f_0
I. $v_0\,=\,10\,ms^{−1}$ and $v\,=\,5ms^−1$
II. $v_0\,=5\,ms^{−1}$ and $v\,=\,10ms^{−1}$
III. $v_0\,=\,10\,ms^{−1}$ and $v\,=\,10\,ms^{−1}$
A. $I$ only
B. $ III$ only
C. $I$ and $II$ only
D. $I$ and $III$ only
参考答案: A
本题详细解析:
Explanation: When the observer and source of the wave are approaching each other, the observed frequency is greater than the frequency of the produced wave. There is no relative motion between the car and the car driver. Therefore, f is equal to the frequency of the sound of the horn. Since the observed frequency is greater than the original frequency of the sound of the horn, there should be a relative approach between the car and the cyclist. This can only happen when the car has a greater speed than the cyclist according to the given figure
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