A train at rest emits a sound at a frequency of 997 Hz. An observer in a car travels away from the sound source at a speed of 30.9 m/s. What is the frequency heard by the observer? Assume the speed of sound in air to be 346 m/s.
Answer in units of Hz.

Aspecified volume of space contains an electric field for which the magnitude is given by e=e0cos(ωt). suppose that e0 = 20 v/m and ω = 1.0 × 107 s−1. part a what is the maximum displacement current through a 0.80 m2 cross-sectional area of this volume? express your answer with the appropriate units. idisp,max i d i s p , m a x = nothing nothing request answer part b how would this area have to be oriented relative to the electric field to get this maximum displacement current?