I just saw this \"trick\" where a cup of water is turned over onto a table witho
ID: 2283907 • Letter: I
Question
I just saw this "trick" where a cup of water is turned over onto a table without spilling (using a piece of cardboard. After removing the cardboard from underneath the cup, the person then removes the cup in a particular way (lifts straight up and twists) and lo and behold, the water stays in it's position as if the cup were still there!? (watch the video to fully understand) Is this really possible? If so, and the real question I'm looking to have answered is, how?
After further research it appears that deionized water is needed as well.
Explanation / Answer
Let's split up the forces, it gives an easier view on what should happen.
Horizontal Forces
What we see is a centrifugal force.
Centrifugal force (from Latin centrum, meaning "center", and fugere, meaning "to flee") represents the effects of inertia that arise in connection with rotation which are experienced as an outward force away from the center of rotation
So, outward force away from the center of rotation. This means that the water would only be able to appear in place if there is a force in the opposite direction, which is known as friction. Where is the friction if you take the glass away? There is no friction anymore, thus that video shows special effects. ;-)
Vertical Forces
There's also the gravitational force. What would keep the water up so long? Nothing.
Furthermore, if you look at his other videos, you can confirm it's CGI... :-)