Question

You were driving your car on the airport road on a hot summer day at a speed of 88 ??/ℎ. You look on the opposite side of the highway and you see a fast Lekhwiya vehicle coming towards you. The Lekhwiya car transmits a siren of 2538 ??. However, when you receive the siren sound and try to measure the frequency, you compare it with the frequency of a tuning fork. As a result, you counted 12 beats every 3 ???????. If the tuning fork frequency is 3000 ??, What is the speed of the Lekhwiya car? Assume that day the temperature under direct sun was ? = 328 ?.

Answer 1

V of your car=88*5/18

=24.44m/s

frequency of lekwiya car siren=2538hz

Let speed of lekhwiya car be V

Taking Velocity of sound at 328K=330m/s

Using doppler effect frequency detected by you=2538(330+24.44)/(330-V)

Beat frequency=4beats/s

So the detected frequency may be 3004hz or 2996hz

Using 3004 hz

3004=2538(330+24.44)/(330-V)

330-V=299.45

V=30.54m/s

Using 2996Hz

2996=2538(354.44)/(330-V)

V=29.74m/s

The above 2 values may be the possible speeds of lekhwiya car