Atrain is moving toward the station at a speed of 25 m/s. its horn emits a sound of frequency 600 hz. (a) calculate the frequency detected by a person standing still at the station. (use 345 m/s for the speed of sound.) (b) as the train moves away, still blowing its horn at the same frequency as before, the observer hears a frequency of 567 hz. calculate the new speed of the train.

(a) 646.9 Hz

The formula for the Doppler effect is:

where

f = 600 Hz is the real frequency of the sound

f' is the apparent frequency

v = 345 m/s is the speed of sound

is the velocity of the observer (zero since it is stationary at the station)

is the velocity of the source (the train), moving toward the observer

Substituting into the formula,

(b) 20.1 m/s

In this case, we have

f = 600 Hz is the real frequency

f' = 567 Hz is the apparent frequency

Assuming the observer is still at rest,

so we can re-arrange the Doppler formula to find , the new velocity of the train:

and the negative sign means the train is moving away from the observer at the station.

tube or goog will be great resources to find the answer to the question that you're asking

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.