Question

The frequency of the siren of an ambulance is 900 and is approaching you. You are
standing in a corner and observe a frequency of 960 . What is the speed of the ambulance
(in ℎ) if the speed of sound is = 340 /?

Answer 1

Speed in mph= 85mph

Speed in kmph= 0.085 kmph

Explanation:

• Actual Freuqency(f1)=900hz
• Observed Frequency(f2)=960hz
• Speed of sound(v)=340m/s

Therefore,

we know,

$w = \frac{v}{f}$

So,

Wavelength of f1 (w1)=

$\frac{340}{900}$

&

Wavelength of f2 (w2)=

$\frac{340}{960}$

Speed of Ambulance= (w1-w2) m/s

$= \frac{340}{900} - \frac{340}{960} \\ \\ = \frac{5440 - 5100}{14400} \\ \\ = \frac{340}{14400} \\ \\ = \frac{17}{720}$

The Ambulance is moving at 17/720 m/s

Answer:

Speed in mph= 85mph

Speed in kmph= 0.085 kmph