1. The problem statement, all variables and given/known data A French and a U.S. submarine are moving directly towards each other during manoeuvres in still water. The French submarine is moving at 50.0 km.hr-1. It sends out a sonar signal at 1100.0 Hz. The frequency detected by the French submarine (reflected back from the U.S. submarine) is 1222 Hz. How fast is the U.S. submarine travelling towards the French submarine? Assume the velocity of sound in sea water is 1500 ms-1. 2. Relevant equations 3. The attempt at a solution I tried making one up lol. f`= f / ((1-(v_F + v_US)/v) Where v_F is the velocity of French and v_US is american, v is speed of sonar signal, f = frequency of sonar signal, so i rearranged to find v_US but Im 100% sure this is not the way to do it.