A racing car has a siren and is speeding with the speed u = 306 km / h . The frequency of the siren is v 0 = 40 Hz . Ahead of it there is another car with exactly the same siren (this car is at rest

Question

A racing car has a siren and is speeding with the speed u = 306 km / h . The frequency of the siren is v 0 ​ = 40 Hz . Ahead of it there is another car with exactly the same siren (this car is at rest). Each of the drivers distinguishes the sound of siren of another car, because it is of higher frequency than the sound of his own siren. Take the speed of sound in air as 340 m/s.

TestHub · Accepted Answer

u = 306 × 18 5 ​ = 85 m / s Speeding driver hears the rest car: f ′ = 340 340 + 85 ​ × 40 = 50 Hz , beats = 10 Hz (B) Rest driver hears the speeding source: f ′′ = 340 − 85 340 ​ × 40 = 3 160 ​ Hz , beats = 13.33 Hz (C) Answers (B, C)

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JEE Advanced 2027 (Class 12)