일반물리학 1 — Waves-II: Problem 31

31 In Fig. 17-29, a French submarine and a U.S. submarine move toward each other during maneuvers in motionless water in the North Atlantic. The French sub moves at the speed \(v_F = 48.00 \text{ km/h}\), and the U.S. sub at \(v_{US} = 72.00 \text{ km/h}\). The French sub sends out a sonar signal (sound wave in water) at \(1.560 \times 10^3 \text{ Hz}\). Sonar waves travel at \(5470 \text{ km/h}\). (a) What is the signal's frequency as detected by the U.S. sub? (b) What frequency is detected by the French sub in the signal reflected back to it by the U.S. sub?