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Flip cup and table conditions

  1. Jul 21, 2014 #1
    Hi everyone, first time post here. Sorry if this isn't the place to ask, but I'm looking to settle disagreement and thought someone here might have the knowledge to set me straight. This is a slightly off color question to start with, and my lack of expertise in any science is not helping the way I phrase anything I'm sure, so sorry in advance.

    So every week a friend and I play in a flip cup tournament. (Played with water, small gift certificate if you win, just a nice way to break up the week)

    For anyone unfamiliar, flip cup is a game where you take plastic cups place them right side up, hanging slightly over the edge of a table or other playing surface. The goal is to get the cup to rest upside down on the table by applying force to the bottom of the cup that is hanging over the edge of the table. (Most instances of the game involve you drinking something out of the cup first, but that's not really pertinent here) Here's a 1min video that explains the concept.

    Anyway, it's my position that having a small puddle of water on the table is beneficial to getting the cup to come to rest upside down. Her position is that it doesn't help, and that it's gross. I am unable to offer any concrete reasoning and my gut/perceived success using water is not sufficient for me to press for playing on a wet table. (It is a little gross) I do however firmly believe that a small puddle of water in the area where your cup begins to land upside down is in fact a benefit, and would help our chances in getting some free food for the night via the gift certificate winnings. I just lack the educational background or applicable knowledge to prove it. (or disprove as the case may very well be)

    So here is my basic thinking, if anyone here is willing to take the time to point me in the right direction or do anything to help I would greatly appreciate it. It really seems that having a shallow "coat" of water on the playing surface where you are attempting to land your cup upside down is beneficial. It sure seems like it helps, and while I have theories as to why, its obvious we need some outside expertise for a definitive answer. My perception is that one or more of a few possibilities are at play here and might explain my apparent success in having water on the table. Or I'm completely wrong.

    1) The water helps stabilize the cup faster. I'm not sure how, but it could, right? Perhaps the water's viscosity slows the cups lateral movement enough that gravity takes care of the rest in a situation where it otherwise may have continued to slide over the edge of the table or simply toppled over?

    2) Since it's the open end of the cup landing in the water, is at all possible that water, rim and air movement combine to form suction or some kind of stabilizing force on the cup that would not otherwise be present?

    I realize this is probably silly to many of you, and I'm not trying to be impertinent in posting this, I assure you I'm asking sincerely. I doubt I'll be allowed to let the puddles to form regardless :P but at this point its about satisfying my curiosity, whether my perception has any validity to it or not, more than it is about winning flip cup. (Although it would be nice)
  2. jcsd
  3. Jul 21, 2014 #2


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    1. It doesn't have anything to do really with the viscosity of water; the film won't lower friction in the lateral direction. Actually, the sticking effect you sometimes notice between wet objects is do pressure conditions, air isn't as readably able to flow between the two objects surfaces, creating a vacuum like effect that sticks the objects together.

    2. Sort of, see above. A simple illustration of this effect can be had with a smooth surface and a glass cup, tip the cup in one direction dry than repeat with a wet bottom. Notice the difference?

    I'm not sure of the effect on red solo cups, or more importantly to you the rim of red solo cups. You're only worried about motion in two dimensions here and it's possible that the displacement of the film as the cup lands may have more effect in preventing tip overs in the y direction. Whether or not a low pressure area can be created around the rim of the cup when it lands, I’m not sure.

    Why not practice some at home, it’d be easy to test which works better for you.
  4. Jul 21, 2014 #3
    Thanks for your answer Student100! Haha, I actually did run some trial and error at home and confirmed that the water seemed to help my average, though unfortunately I'm not very skilled so chance still might have made all the difference, something my friend was quick to point out. In either case she doesn't believe me, and didn't seem amenable to conducting her own experiment so I needed something concrete to point to when making my case.

    That quick glass illustration does the trick! Obviously the conditions aren't exactly the same, but I'm going to use that effect to make the argument that it comes into play during shots where our cup might be close to somersaulting completely over; that it could sometimes tip the balance (giggle) in our favor. I'm sure she'll still disagree, but at least this demonstrates my theory is valid enough to warrant further exploration!
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