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Car horn A car horn vibrates at a frequency of 250 Hz. Determine the frequency a stationary observer hears as the car (a) approaches at a speed of 20 m/s and (b) departs at 20 m/s. If the car is stationary, what frequency is heard. (c) by an observer approaching the car at 20 m/s and (d) by an observer departing from the car at 20 m/s?
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