98.18: When a train is at rest, both a pasxf4 2t(ddaee- senger 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 2 d4et(dea-fx 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 y.q-dnlw8mn: s gd(w i1p+h y+the left at 20 m/s 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 frequency of the sound by the driver of the car? Assume the vehicles are mo wql(pnmw. :8+ -1+ddhs ngyiyving directly away from each other on a $20.0^{\circ}C$ day

  17.39: A point wave source t /.7jcp7,03cg*plty g0lrp f 0b ryorwravels along 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 brick walv8ds+6jvsnlsfv6 - u 4l in a crash test at 30 m/s. The horn is emitting a sound with frequency 250 Hz as it approaches the wall. If the a4- lss v+ 86vnvju6dfsir 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?