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An ambulance is driving towards the hospital at a velocity of 99.9 km/h and emitting a steady 786 Hz sound from its siren. The sound reflects off the front of the hospital and is received by the same ambulance. What frequency does the ambulance hear from the reflection, in addition to its own siren? The speed of sound on this day is 343 m/s.

Answer :

Answer:

The frequency is 924.3 Hz.

Explanation:

Given that,

Velocity of ambulance = 99.9 Km/h

Sound frequency = 786 Hz

We need to calculate the frequency

Using formula of frequency

[tex]f=f_{0}(\dfrac{v+v_{0}}{v-v_{0}})[/tex]

Where, v = speed of sound

v₀ = velocity of observer

f₀ = Observer frequency

Put the value into the formula

[tex]f=786\times(\dfrac{343+99.9\times\dfrac{5}{18}}{343-99.9\times\dfrac{5}{18}})[/tex]

[tex]f=924.3\ Hz[/tex]

Hence, The frequency is 924.3 Hz.

Answer:

924.376 Hz

Explanation:

Data provided in the question:

Velocity of the ambulance, v = 99.9 km/h = [tex]99.9 \times\frac{5}{18}[/tex] m/s

= 27.75 m/s

Frequency of the sound, f₀ = 786 Hz

Speed of the sound, V = 343 m/s

Now,

Using the Doppler's effect formula, we have

Frequency heard = [tex]f_0\times[\frac{V+v}{V-v}][/tex]

Thus,

Frequency heard = [tex]786\times[\frac{343+27.75}{343-27.75}][/tex]

or

Frequency heard = 786 × 1.176

or

Frequency heard = 924.376 Hz

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