A train moves towards a stationary observer with speed 34 m/s

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

Problem

A train moves towards a stationary observer with speed 34 m/s. The train sounds a whistle and its frequency registered by the observer is

f_1

. If the speed of the train is reduced to 17 m/s, the frequency registered is

f_2

. If speed of sound is 340 m/s, then the ratio

f_1/f_2

is: (1) 18/17 (2) 19/18 (3) 20/19 (4) 21/20