In which of the following will you (the observer) hear a higher frequency than w
ID: 1471838 • Letter: I
Question
In which of the following will you (the observer) hear a higher frequency than what the source is emitting? Choose all that apply.
A police car with its siren on is moving towards you while traveling 50 mph. You are moving away from it while traveling 50 mph.
A fire truck with its siren on is circling you. You are stationary.
An ambulance with its siren on is moving away from you while traveling 40 mph. You are stationary.
A train with its horn blaring is stationary. You are moving towards it while traveling 50 mph.
A marching band playing the 1812 Overture is moving away from you while traveling 40 ft/min. You are moving towards it while traveling 50 ft/min.
Explanation / Answer
When the source is approaching, the frequency
f= [v/(v-vs)]* fsource
Vs is postive if relative distance between source and observere is getting less.
So answer to the question are.
A train with its horn blaring is stationary. You are moving towards it while traveling 50 mph.
A marching band playing the 1812 Overture is moving away from you while traveling 40 ft/min. You are moving towards it while traveling 50 ft/min.
Between, when source is encricling you, relative distance stays the same, vs=0. No frequency change.