Wave Mechanics Question 680
Question: Two trains are moving towards each other with speeds of 20m/s and 15 m/s relative to the ground. The first train sounds a whistle of frequency 600 Hz. The frequency of the whistle heard by a passenger in the second train before the train meets, is (the speed of sound in air is 340 m/s)
Options:
A) 600 Hz
B) 585 Hz
C) 645 Hz
D) 666 Hz
Show Answer
Answer:
Correct Answer: D
Solution:
[d] $ v’=v( \frac{v+v _{D}}{v-v _{S}} ) $ Here, $ v=600Hz,v _{D}=15m/s $
$ v _{s}=20,m/s,v=340m/s $
$ \
Therefore v’=600( \frac{355}{320} )\approx 666,Hz $
BETA
