wave_mechanics critical_thinking Question 50
Question: A racing car moving towards a cliff, sounds its horn. The driver observes that the sound reflected from the cliff has a pitch one octave higher than the actual sound of the horn. If $ v $ is the velocity of sound, then the velocity of the car is
[KCET 2002; CBSE PMT 2004]
Options:
A) $ v/\sqrt{2} $
B) $ v/2 $
C) $ v/3 $
D) $ v/4 $
Show Answer
Answer:
Correct Answer: C
Solution:
Frequency of reflected sound heard by driver $ {n}’=n( \frac{v+v _{O}}{v-v _{S}} ) $ It is given that $ {n}’=2n $ Hence, $ 2n=n( \frac{v+v _{car}}{v-v _{car}} ) $
Therefore $ v _{car}=v/3.
$
BETA
