A car is parked 20.0 m directly south of a railroad crossing. A train is approac

Question

A car is parked 20.0 m directly south of a railroad crossing. A train is approaching the crossing from the west, headed directly east at a speed of 49.5 m/s. The train sounds a short blast of its 304-Hz horn when it reaches a point 20.0 m west of the crossing. What frequency does the car's driver hear when the horn blast reaches the car? The speed of sound in air is 343 m/s. (Hint: Assume that only the component of the train's velocity that is directed toward the car affects the frequency heard by the driver.)
__________________ Hz

Explanation / Answer

Given that Car is 20m from south Velocity of trainv =60m/s Since both are crosing normal to each othes Along SW or SE The angle = 45 deg They meet along the diagonal line The velocity of train relative to car, Vs=vcos45 Vs = 60(cos 45) = 42.4 m/s towards the car When the source is taken as train When the soure *Train) move towardes the observer(in car) The frequency does the car driver hear is from the doppler effect is given by n' = n(V+Vs)/V      = 304(343 + 42.4) / 343        = 341.57 Hz         ˜342 Hz Given that Car is 20m from south Velocity of trainv =60m/s Since both are crosing normal to each othes Along SW or SE The angle = 45 deg They meet along the diagonal line The velocity of train relative to car, Vs=vcos45 Vs = 60(cos 45) = 42.4 m/s towards the car When the source is taken as train When the soure *Train) move towardes the observer(in car) The frequency does the car driver hear is from the doppler effect is given by n' = n(V+Vs)/V      = 304(343 + 42.4) / 343        = 341.57 Hz         ˜342 Hz Given that Car is 20m from south Velocity of trainv =60m/s Since both are crosing normal to each othes Along SW or SE The angle = 45 deg They meet along the diagonal line The velocity of train relative to car, Vs=vcos45 Vs = 60(cos 45) = 42.4 m/s towards the car When the source is taken as train When the soure *Train) move towardes the observer(in car) The frequency does the car driver hear is from the doppler effect is given by n' = n(V+Vs)/V      = 304(343 + 42.4) / 343        = 341.57 Hz         ˜342 Hz

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