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Friction coefficient

  1. Jun 17, 2003 #1
    Someone was talking to me about a waterslide. And she said that when the waterslide they would slide a lot faster then if the slide was wet. I was thinking about this, but the only thing i can think of is that the coefficient of friction on dry fiberglass is less then that of water on fiberglass, but that doesnt sound right because my bathtub doesnt seem slipperier(?) when its dry. Anyone have any ideas?
  2. jcsd
  3. Jun 17, 2003 #2
    I do beleive that your correct in thinking that the waterslide has more friction when its dry than when its wet, otherwise there would be no need for water on the water slide, would there, also just think of the album by Bon Jovi "Slippery When Wet".
  4. Jun 17, 2003 #3
    well i think the end of the ride ended with a lot of swearing, cuz going faster gave them a lot of bruises cuz they were flying around in there. But i dont think rides would put water in them to slow it down.
  5. Jun 17, 2003 #4
    Nah they wouldnt, should try to get some smarter people in this thread to explain it better, i know (well think i know) that the water will increase the speed because it provides a surface with less friction than that of the normal surface on which you slide on, but im not sure how to explain it in a better way than that.
  6. Jun 17, 2003 #5


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    I'm afraid I don't quite understand this statement. Are there perhaps some words missing from it?

    Was your friend telling you that they would slide faster when the slide was dry than they would when it was wet?

    If they were going down a waterslide while it was dry, I should think they'd have more than some bruises to worry about. I once grabbed the sides to slow my descent (the person in front of me had not gotten off), and burned blisters into my hands with less than 1/2 second of contact. I hate to think what such contact would do to the posterior! Was this a slide with those rubber mats to sit on?
  7. Jun 17, 2003 #6
    The bottom of your tub

    is specially treated so that it won't be slippery when wet. But if the slide is treated, it will be so that it will be more slippery when wet.
  8. Jun 18, 2003 #7
    Try to imagine this :
    Get a Latex ball, and put it on a dry waterslide.
    Then, get the same Latex ball, and put it on the same waterslide, but this time, let it be wet.
    You will see that in the first case, the ball will not slip (well, it can slip, but the chance of it sliping will be less than the chance when the waterslide is wet).
    Draw an illustration, and see what are the forces holding the ball, you will notice there is ONLY friction holding the ball (actually, a similiar experiment is used to calculate the coefficient of friction of matters).
    On the other hand, in the case when the waterslide was wet, the ball will slide (again, it might not slide, but its chance of sliding will be bigger), if you try to notice the change in forces between case1 and case2, you will see that only a change in friction is possible (since the weight of the ball will not change, the normal force will not change (remember, you are on the same waterslide), so only friction will change).
    So it is clear that the friction force on the ball changed when water was added, and since the normal didn't change, then the coefficient of friction is what is changed (remember that friction force depends on normal force and coefficient of friction).
    Does this help ?
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