Question: [![Windmill](https://i.stack.imgur.com/txg2H.jpg)](https://i.stack.imgur.com/txg2H.jpg)

I am trying to design the windmill blades (the green part) in Solidworks but am having trouble since the radius of curvature for the blades varies at different points. I tried bending it as a sheet metal, but am having a lot of difficulty. Any ideas?

Answer: 
The classic example of a frame of reference in which gravitational forces *disappear* is called a *freely-falling* reference frame.

This is what you get when in deep space, or in orbit around the earth, or when falling off a tall building or down a mine shaft on earth.

In a freely-falling reference frame, pendulums do not swing because all the (mg) terms vanish.
it is called free float. And Einstein used it as an intuition leading to his theory of general relativity. In a small local spacetime no physical ebservation or experiment can tell the difference between weightlessness and free float.

the picture is from A Jurney into Gravity.. by John A Wheeler.

It is said that he considered this was one of his the happist thought. [![Einstein free floating room](https://i.stack.imgur.com/ZHFMt.jpg)](https://i.stack.imgur.com/ZHFMt.jpg)