試題詳解

58. Two cars are approaching to each other. Car A moves at speed v_A = 108.0 km/hr, and the car B at v_B = 72.0 km/hr. The car A sends out a horn sound traveling in air with speed of 343 m/s. The horn’s sound frequency as detected by the car B is 1000 Hz. The horn’s sound frequency that car A sends out is __________.
(A) 1212 Hz
(B) 1154 Hz
(C) 948 Hz
(D) 862 Hz
(E) 821 Hz