1. The problem statement, all variables and given/known data A 60 tonne submarine, intially travelling forward at 1.5 m/s, fires a 500 kg torpedo striaght ahead with a velocity of 21 m/s in relation to the submarine. What is the velocity of the submarine after it fires the torpedo? Answer: 1.3 m/s [forward] 2. Relevant equations 1 ton = 1000 kg p = p' 3. The attempt at a solution p = p' (60000)(1.5) = (500)(22.5) - (59500)(Vs') Vs' = -1.32 m/s I don't understand why I am getting that answer, as the answer is actually forward. Because doesn't the torpedo going forwards cause the submarine to move backwards. Other than that, can you guys tell me whether I set it up right? Like the speed of the torpedo should be 22.5 m/s right, since the submarine is already travelling at 1.5 so it gets added? Also, the final mass of submarine shud be 59 500 kg, since the torpedo is no longer attached to it? Thanks.