I hope I'm posting this in the right section. What follows is not an actual homework problem, but it is a problem that might be similar to a textbook problem, and it involves calculus that I do not understand. The question is as follows: 1. The problem statement, all variables and given/known data A bullet is fired from a gun. As soon as it leaves the barrel, the bullet begins to decelerate due to air resistance at a rate defined by the following equation: a = -kv2 The variable "a" is (negative) acceleration. The variable "v" is instantaneous velocity. The variable "k" is simply a constant that relates to the particular properties of the bullet. From this equation, write a function that describes the time it will take the bullet to travel x distance. ------ Now, I have asked this question before, and I actually was given a solution by someone at one point that works. It involved integrating the given function twice, but truthfully, I don't understand it at all, and I would really like to. I am hoping that someone on this forum might be able to help me understand the calculus involved with this sort of thing. 3. The attempt at a solution The solution is this: t = (1/(V * k)) * (exp(D * k) - 1) "V" is the initial velocity of the bullet (i.e., the muzzle velocity); "k" is the constant from the original equation; "D" is the distance the bullet traveled; and "exp" is just shorthand for the exponential equation (i.e., e to the power of D * k). This solution works. I have tested it. But I have no idea how it was obtained, and it's driving me crazy. If anyone can help me understand it, I would be most appreciative!