1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Surface of a liquid behaving like a stretched membrane

  1. Sep 25, 2013 #1
    The surface of any liquid behave like a stretched membrane. Is it because of surface tension or all the possible forces acting on a liquid molecule at the surface? I asked this question because if the furface behaves stretched because of surface tension then it means that the forces making the surface stretched are only horizontal. Whereas if the surface if behaving like a stretched membrane because of all the forces on the molecule on the surface this means the forces going into the bulk of the liquid also make it stretched. I just can't imagine the latter situation as in if we have a streched bubble membrane. It is stretched because of all the horizontal forces appears good rather than stretched because of all forces because if all the forces pull it, won't the bubble membrane burst as there would be an excess downward force?( Since there is a net force on the molecule at the top of the membrane which tries to bring the molecule at the top into the bulk.) But since the bubble membrane doesn't burst it means that it gets stretched only by the horizontal forces?
  2. jcsd
  3. Sep 25, 2013 #2


    User Avatar
    Gold Member

    Why? That would mean that INSTANTLY when the surface is deformed away from horizontal, the surface tension would no longer support whatever it is supporting. Doesn't seem to make sense.
  4. Sep 25, 2013 #3
    When surface is deformed then surface tension would be along the tangent to the curve(shape of depression which the object made). So it would be able to support the object. Besides its nowhere written that surface tension supports the body in consideration. Is it?
    Last edited: Sep 25, 2013
  5. Sep 25, 2013 #4
    Yes. This is a correct assessment. In the case of a bubble, there are two surfaces (inside and outside of the bubble thickness), so you have to take into account the surface tension at each surface.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted