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timetraveller123

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## Homework Statement

Two trains approach the train station from opposite sides each moving at an initialvelocity of 120 km/h with respect to the station and slowing down to a halt in 20seconds. If both trains are whistling at 5000 Hz, ﬁnd the distance between the zeroand ﬁrst order maxima as a function of time.

so this is the question:

when they say zero and first order maxima they mean it only lies on the x-axis right meaning the zero order maxima is at the centre of the two trains and the first order maxima is at distance d away where the extra length traveled is exactly a wavelength so i did the question just for the part when the trains are not decelerating ie t=0 and my solution does not match the given one please help or is the first order maxima in the y direction

## Homework Equations

f = f

_{o}[c/c-v] --- doppler effect for train approaching

c= 331m/s

λ = c/f

v = 120/3.6 m/s

the given solution is at t =0 the distance between the zero and first order is 893/60000 m

## The Attempt at a Solution

the first order is offset to one side by distance d so

2d is the extra length traveled the sound wave coming from the other side hence

2d=λ

2d = c/f

2d = c(c-v)/(2c f

_{o})

plugging in gets me 893/30000 which is twice of correct answer please help

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