AP Physics 1 Question 263: Answer and Explanation

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Question: 263

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

Explanation:

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