Question

The Doppler formula for the frequency detected can be written f = f’ (v - vD) / (v - vS), where f’ is the frequency emitted, v is the speed of sound, vD and vs are suitable components of the detector and source velocities. (vD and vs can be of either sign depending on the direction of the motion relative to the S-D axis.) Suppose the source is traveling at 5 m/s away from the detector, the detector is traveling at 7 m/s toward the source, and there is a 3 m/s wind blowing from the source toward the detector. The values that should be substituted into the Doppler shift equation are (in m/s):

a. vD = 10 vs = 2 b. vD = -7 vs = -5 c. vD = -7 vs = 5 d. vD = 4 vs = 2 e. vD = -10 vs = -8

Answer 1

he correct answer is c. vD = -7 vs = 5.

The Doppler shift equation is:

f = f' (v - vD) / (v - vS)

Where:

f is the frequency detected

f' is the frequency emitted

v is the speed of sound

vD is the velocity of the detector

vs is the velocity of the source

In this case, the source is traveling at 5 m/s away from the detector, the detector is traveling at 7 m/s toward the source, and there is a 3 m/s wind blowing from the source toward the detector.

The velocity of the detector is negative because it is moving towards the source. The velocity of the source is positive because it is moving away from the detector.

Therefore, the values that should be substituted into the Doppler shift equation are:

vD = -7

vs = 5

Explanation: