A car's horn emits sound having a dominant frequency of 2400 Hz . Determine the apparent dominant frequency heard by a person standing on the road ahead of the car, given that the car approaches at 18.0 km/h . The speed of sound in air is 340 m/s .

Step-by-step solution

The speed of the car (source) is v_s = 18.0 km/h = 18.0 5 18 m/s = 5 m/s . The observer is stationary, so v_o = 0 . Using the Doppler effect formula for a source approaching a stationary observer: f' = f ( v v - v_s ) Substituting the given values: f' = 2400 ( 340 340 - 5 ) f' = 2400 ( 340 335 ) f' 2435.8 Hz Rounding to the nearest integer, the apparent frequency is 2436 Hz .