AP Physics 1 Question 263: Answer and Explanation
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9. A bat emits a 40 kHz "chirp" with a wavelength of 8.75 mm toward a tree and receives an echo 0.4 s later. How far is the bat from the tree?
- A. 35 m
- B. 70 m
- C. 105 m
- D. 140 m
Correct Answer: B
The speed of the chirp is
If the distance from the bat to the tree is d, then the wave travels a total distance of d + d = 2d (round-trip distance). If T is the time for this round-trip, then