1. The problem statement, all variables and given/known data The position function of a spaceship is r(t) = (3+t)i + (2+ln t)j + (7 - 4/(t^2+1)k and the coordinates of the space station are (6,4,9). If the spaceship were to "coast" into the space station, when should the engines be turned off? 2. Relevant equations The relevant equations are r' = velocity, and r'' = acceleration. 3. The attempt at a solution I am really not sure how to go about solving this problem. So, this means that r" is zero but then there is still velocity? So, if r' is i + 1/tj + 8t/(t^2+1)^2k. r" = -1/t^2 + (8(t^2+1)^4 - 16t^2(t^2+1))/(t^2+1)^4. But then I am not sure what to do after that. Thanks!!