Question

A bat emits an ultrasonic sound wave at 35 Hz and receives a reflected signal in the form of an echo 0.20s later. If the speed of sound in air is given to be 330 ms-1 , how far is the bat from the object?
33,45,106or1650m??

Answer 1

A bat emits an ultrasonic sound wave at $35\mathrm{Hz}$ and receives a reflected signal in the form of an echo 0.20s later. If the speed of sound in air is given to be 330 ms-1, how far is the bat from the object?

33,45,106or1650m??

Solution:

$V = 330\frac{m}{s}, t = 0.20s$

Before the sound returns to the bat as an echo, it passes the distance from the bat to the object and from the object back to the bat:

$$t = t _ {b \rightarrow o} + t _ {o \rightarrow b}$$

The distance to the object and back to the bat:

$$d _ {b \rightarrow o} + d _ {o \rightarrow b} = 2 d$$ $$2 d = t \cdot V$$ $$d = \frac {t \cdot V}{2} = \frac {0 . 2 s \cdot 3 3 0 \frac {m}{s}}{2} = 3 3. 0 m$$

Answer: the bat is on the distance $33\mathrm{m}$ from the object.