 Classical Mechanics

Doppler Effect As shown in the above diagram, person $$A$$ driving a car with speed $$v_A = 17 \text{ m/s}$$ hears a siren sound with frequency $$f_ A = 737 \text{ Hz}$$ at a distance of $$d = 141 \text{ m}$$ behind him, coming from an ambulance chasing his car with speed $$v_{am} = 34 \text{ m/s}.$$ What is the approximate frequency of the siren sound heard in the ambulance?

Assumption

• The speed of sound is $$u = 340 \text{ m/s}.$$ An ambulance sounding a siren of frequency $$f_{am} = 687 \text{ Hz}$$ is traveling towards a vertical reflecting wall with a speed of $$v_{am} = 15 \text{ m/s}.$$ If the wall is moving in same direction as the ambulance with a speed of $$v_w = 5 \text{ m/s},$$ what is the approximate beat frequency heard by the driver of the ambulance?

Assumption

• The speed of sound is $$u = 340 \text{ m/s}.$$

A person is riding a merry-go-round which has a radius of $$r = 3 \text{ m}$$ and an angular speed of $$\omega = 3 \text{ rad/s}.$$ If the person starts to blow a whistle of frequency $$f= 485 \text{ Hz},$$ what is the approximate highest frequency heard by a listener at rest a long distance away?

Assumption

• The speed of sound is $$u = 340 \text{ m/s}.$$ As shown in the above diagram, person $$A$$ drives a car with speed $$v = 16 \text{ m/s}$$ at a distance of $$d = 119 \text{ m}$$ away from an ambulance standing still and sounding a siren with frequency $$f_ A = 763 \text{ Hz}.$$ What is the approximate frequency of the siren sound heard in the car?

Assumption

• The speed of sound is $$u = 340 \text{ m/s}.$$ As shown in the above diagram, person $$A$$ hears an ambulance which heads towards him at a speed of $$v = 14 \text{ m/s}$$ sounding a siren with frequency $$f_A = 775 \text{ Hz}$$ at a distance of $$d = 104 \text{ m}$$ away from him. What is the approximate frequency of the siren sound heard in the ambulance?

Assumption

• The speed of sound is $$u = 340 \text{ m/s}.$$
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