98.18: When a train is at rest, both a passv d0li(x1ffoos(,ej aw8o,y4enger on the train and a ticket seller on the station agree that the trains whistle produces sound at a frequency of 120 Hz. When the train is moving away from the station at 15 m/s, the passenger hears a frequency of _____ Hz and the ticket 1lifyoxvw,( oe4a ,0jd(f s 8oseller hears a frequency of ____ Hz.

  08.18: A car is moving to the left at 20 m/s while a truck is mo c ;x3 pic:o*l;owp7siving to the right at 25 m/s. If the truck emits a sound of frequency 5000 oil ;x;woc3* 7ip:c spHz, what is the perceived frequency of the sound by the driver of the car? Assume the vehicles are moving directly away from each other on a $20.0^{\circ}C$ day

  17.39: A point wave source travels along the x-axis at co19gt)qeef0h p nstant speed $v_s$. Stationary observers on the x-axis measure the wavelength of the waves that they receive. The ratio of the wavelength measured at a location behind the source to the wavelength measured at a location in front of the source is 1.50. If the wave speed is v, what is the source speed $v_s$?

  02.47: A car heads toward a brickt)+of3j9b +yhftw -b ;q ir.en wall in a crash test at 30 m/s. The horn is emit+bhwq ntj r-f; )feb3yt9io. +ting a sound with frequency 250 Hz as it approaches the wall. If the air is still and the speed of sound in air is 340 m/s, what beat frequency from the horn would the driver of the car detect?