Hi there... As English is not my native language I want to apologise up front for any mistakes. I have tried asking my question in a local Dutch forum, but I have not received a satisfactory answer yet. So, I thought I will try internationally. Imagine a fast spinning wheel, like in a gyroscope. Let's assume there's no friction of any kind, so if you let it it will keep spinning at the same speed. Now you tilt the spinning wheel by 90 degrees. Of course it resists this movement (I think conservation of angular momentum is the right word?), but you don't allow it to move in any other way than the 90 degrees tilt that you intend. To move the wheel this way you put in energy. You have to overcome the resistance all the way. My question is: Where does this energy go? I don't mean any heat resulting from friction. You put in energy, you add energy to the spinning-wheel-system, where does it go? Does the speed (rate?) of spinning change? Decelerate? Accelerate? I hope my question is clear, and I'm looking forward to any replies. Thank you.