Alright, I'm doing a dynamical magnetism problem for my physics class. I've got it almost done except I need to take the derivative of 1/x^3 with respect to time. X in this case is a variable for meters, I want to turn this into an expression with velocity (Velocity is given) but I'm not sure what that is. d(1/x^3)/dt = ? I'm pretty sure its not just 1/v^3 but that would be nice ^_^. Any help would be appreciated. Would this just be -4x^-3*v?