Puzzles/Physics puzzles/Levitating Straws/Solution
Bend the fourth straw partially in half. Place it around the third straw so that its tip (in the middle of the straw) goes under the piece of paper in the shape of a V. Bend the fourth straw fully in half so it grips the third straw. Lift it up carefully, pulling up the first and second straws as well.
I think a better solution -- it doesn't involve modifying the fourth straw -- is this:
Place the fourth straw through the pyramid under the third straw. This means that the fourth straw goes through both "faces" of the pyramid that adjoin the third straw, and does not go through the face formed by the first two straws.
Holding the fourth straw parallel to the surface of the table and parallel to the face formed by the first two straws, move the fourth straw toward the first two straws. This will push the first two straws away from the third straw.
The third straw will fall. If you have positioned the fourth straw correctly, the third straw will hit the fourth straw rather than falling to the table.
The fourth straw forms a triangle with the first two straws, and the end of the third straw (leaning against the fourth straw) is pointed toward this triangle. Move the fourth straw down a bit and toward the third straw. This will allow the first two straws to fall toward the third straw. The end of the third straw should now go up and through the first two straws.
Now if you lift straight up, the third straw will lock with the first two straws over the fourth straw. You can lift all the straws at once.