Afrench submarine and a u. s. submarine move toward each other during maneuvers in motionless water in the north atlantic. the french sub moves at speed vf-50.0 km/h, and the us. sub at vu,-70.0 km/h. the french sub sends out a sonar signal (sound wave in water) at 1000 hz. sonar waves travel at 5470 km/h. (a) what is the signal's frequency as detected by the u. s. sub? (b) what fre- quency is detected by the french sub in the signal reflected back to it by the u. s. sub? frenche u. s vus fig. 16-22 problem 32.