98.18: When a train is at rest, both a passenger on the train and a tickerd-nm8h1mmt+ss e gm3fglk; 7qf,*i )t 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 stationq1 d-ssk 8+* tieg7ln 3)f,fmgmhm;rm 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/svbr nu:(9iuj m1*rwfcz) b 0cmz8zv5, 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 perceived1ni5 vf rmzb ccumz *( rj8,)uwb:zv09 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-axe)d ac 7c/2,tymkzgq+is 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 towarzqa)ol,xba+ b 7 j.n-rd a brick wall in a crash test at 30 m/s. The horn is emitting a sound with fre,lbqz7+j xnro a.-b)aquency 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?