98.18: When a train is at rest, both a passengeai:j3n z*r0ys,*icjt 9g4v1h x h.pixbtt.1r r 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 th0i vxhjrx1:93pr4c1 a*i. t tn s, bzy.ig*jaway from the station at 15 m/s, the passenger hears a frequency of _____ Hz and the ticket seller hears a frequency of ____ Hz.

  08.18: A car is moving to the left at 20 m/si 8,c8gnyo*mt:oy x8q while a truck is moving to the right at 25 m/s. If the truck emits a sound of frequency 5000 Hz, what is the perceived frequencmq8i ,t8g :no* yycox8y 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 alongdh:e95 zywz )4lmt9vh the x-axis at constant 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 brickbswcw ny 7::t0 wall in a crash test at 30 m/s. The horn is emit0ytsw:c:b nw 7ting 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?