Hi, For my Writing for Engineers class I have decided to take on a feasibility inquiry: "Is it possible to power a NYC subway train using wind turbines atop that same train?" (provided that a NYC subway train requires 2.1 MW of power to run at 55 mph) Now, I have come to the conclusion that this is impossible because of things like air resistance and weight but I am not sure of the fine details. 1- If somone could give me a thorough explanation I would very much appreciate it! I have emailed a professor about this and received the answer: "Any electrical power that you take out of the turbine will add to the 2.1MW that the train draws from the power lines just to move forward at 55mph. Thus, if you connected up some electrical device that consumed 1MW of electricity from the turbine, the train would then draw 3.1MW of power from the power lines. As you draw more power from the turbine, the blades become harder to turn and the wind resistance goes up, causing the train's motor to work harder." 2 - Everything here is understandable in a general sense except why do the turbine blades become harder to turn? If a 55 mph wind is still hitting the turbine, what is making it harder to turn? Now, what if the power lines were not used to power the train with the turbines helping but instead a system of batteries (with the turbines recharging the batteries) were used to power the train? I know that this still would not work. But again, only in a general sense. 3 - A clear explanation as to why this would still not be feasible would be much appreciated! Thank you all in advance!