We have fixed a slant standing rod to a vertical axis, in a way that we can rotate the rod.
Test, whether the straight, slant standing rod gets through the hole cut in the plexi-disc!
The slant standing rod gets through the crooked hole unobstructed.
There is a mathematical explanation for this: if we rotate a line (rod) under a certain angle around an axis that does not cross the line, than this slant line draws a crooked surface, which is called rotating hyperboloid.
If we cut this surface with a sheet having the rotating axis on itself, then we get a hyperbola, just like the one we cut into the plexi-disc. This makes the crooked part of the surface that our line (rod) got through without any obstruction.
