Question

8. What is the frequency heard by a person driving at 15.0 m/s toward a blowing factory whistle (800. Hz) if the speed of sound is 340.6 m/s? (837 Hz) F= (340.6×800)÷(340.6-15)= 836.9 Hz F=836.9 9. From the previous problem, what frequency would he hear after passing the factory if he continues at the same speed? (766 Hz)

Answer 1

Answer:

A) f_o ≈ 836.9 Hz

B) f ≈ 765 Hz

Explanation:

A) To solve this, we will use the formula;

f_o = (v•f_s)/(v - v_p)

Where;

v is speed of sound in air

f_s is frequency of source

v_p is the speed of the person moving towards the whistle.

We are given;

v = 340.6 m/s

v_p = 15 m/s

f_s = 800 Hz

Thus;

f_o = (340.6 × 800)/(340.6 - 15)

f_o ≈ 836.9 Hz

B) to solve this, let's first calculate the wavelength from the formula;

λ = v/f_s

λ = 340.6/800

λ = 0.42575 m

To get the frequency he will hear after passing the factory, we will use the formula;

f = (v - v_p)/λ

f = (340.6 - 15)/0.42575

f ≈ 765 Hz