A traffic policeman stationed on a road blows a whistle that emits a main frequency of 2.00 kHz . Determine the apparent frequency heard by a scooter-driver who is approaching the policeman at a speed of 36.0 km/h . The speed of sound in air is 340 m/s .

Step-by-step solution

The frequency of the source is f = 2.00 kHz . The speed of the observer is v_o = 36.0 km/h = 36.0 5 18 m/s = 10.0 m/s . The speed of sound is v = 340 m/s and the speed of the source is v_s = 0 . Using the Doppler effect formula for an observer approaching a stationary source: f' = f ( v + v_o v ) Substituting the given values: f' = 2.00 ( 340 + 10 340 ) f' = 2.00 ( 350 340 ) f' = 2.00 35 34 2.058 kHz Rounding to two decimal places, f' 2.06 kHz .