In class I've built a Maglev train. In the report we should also cover the theory behind the Maglev train though. I came across the Transrapid train in Germany. I have a question concerning a formula we used in the report. 1. The problem statement, all variables and given/known data We used the following formula: P = Cw×Afront×(density of surrounding air)/2 (see http://en.wikipedia.org/wiki/Transrapid#Energy_requirements) Our teacher wants us to tell what this formula actually derives from (such as p=F/A and F=m×a) We are however unable to solve this. 2. Relevant equations p=F/A, F=m×a and probably many more 3. The attempt at a solution We didn't get much further than what is already said above :/ Thanks in advance.