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Friction on a rainy day

  1. Feb 24, 2014 #1
    A comb run through dry hair attracts bits of paper. What happens if your hair is wet or it is a rainy day?
    I guessed that the comb would stop attracting paper, what bothers me is why. My book says its because if my hair is wet or its a rainy day, the friction between the comb and my hair reduces. I don't understand how exactly that happens. I mean wouldn't the comb still be up against the same amount of roughness on the molecular level.
    Also, I thought the reason could be because when it is wet, there are more H2O molecules around so they get polarised and act as preventive forces in the space between the comb and the paper and thereby prevent the paper from being polarised and hence be attracted towards the comb.
    Does that make any sense? I confused myself while writing this XD
  2. jcsd
  3. Feb 24, 2014 #2


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    Staff: Mentor

    I think hair is hygroscopic, absorbing moisture on humid days then losing some when humidity drops. So the fibres probably swell slightly and become smoother, so maybe friction really is different in damp weather. But I think the main problem is that charges quickly leak away over damp surfaces in humid weather so it doesn't have a chance to build up to the 'crackling' stage.
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