A train approaches a vertical cliff while moving at

PHYSICS · Single correct · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics

Problem

15\,\text{m s}^{-1}

. The driver blows the whistle of frequency

600\,\text{Hz}

and hears the sound directly as well as after reflection from the cliff. If the speed of sound in air is

340\,\text{m s}^{-1}

, what beat frequency does the driver hear? (a)

30\,\text{Hz}

(b)

55\,\text{Hz}

(c)

72\,\text{Hz}

(d)

53\,\text{Hz}