Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What cause an object to float?

  1. May 2, 2007 #1
    From what I gather so far, 2 main concepts determine if an object can float or not: 1) Archimede's buoyancy principle 2) Surface Tension.

    Is the above reasoning correct? Are there any other concept?
     
  2. jcsd
  3. May 2, 2007 #2
    I dont think surface tension has much to do with it.
     
  4. May 2, 2007 #3
    Water strider bug has surface tension to hold it up.
     
  5. May 2, 2007 #4
    I stand corrected.

    I dont think the buoyant force would act on that bug would it?

    If a body displaces fluid then I dont think surface tension would have much of an effect, for example in a boat.
     
  6. May 2, 2007 #5

    Danger

    User Avatar
    Gold Member

    Actually, it does. If you want to have some fun with water bugs, just put a few drops of dish detergent beside them. Poof... straight down. :biggrin:
     
  7. May 3, 2007 #6

    russ_watters

    User Avatar

    Staff: Mentor

    An object that sits on top of a surface of a liquid due to surface tension is not floating. The word "floating" is referring specifically to buoyancy. It's right there in definition #1.

    A water bug is standing on the water, not floating in it.
     
    Last edited: May 3, 2007
  8. May 3, 2007 #7

    Danger

    User Avatar
    Gold Member

    Oops... another terminology problem. :redface:
    While 'buoyancy' refers to Archimedes, I always took 'floatation' to be a combination of various factors that keep an object from submerging. The vanes of a hydrofoil, for instance, are not buoyant... but they 'float' when an appropriate speed is achieved.
     
  9. May 3, 2007 #8

    russ_watters

    User Avatar

    Staff: Mentor

    Where are you from, Danger (your profile says the Twilight Zone, so I'm guessing Canada?)? It could be geogrphical differences in word usage. I wouldn't say any non-displacement vessel floats when it is in that mode (including speedboats).
     
    Last edited: May 3, 2007
  10. May 3, 2007 #9

    Danger

    User Avatar
    Gold Member

    Yeah, it's probably regional. We use the term for lots of different circumstances, such as a car at the top of its suspension travel or a pool ball rolling too far. 'Skating' is used in the same context.
     
  11. May 3, 2007 #10

    russ_watters

    User Avatar

    Staff: Mentor

    Well, wait - the word "float" has different definitions that don't all have to do with the concept of buoyancy - or even liquids. It has forty definitions. You can "float" an idea too, but that may be figuratively connected to the concept of buoyancy...

    It is also a tool for polishing marble (36).

    Maybe I'm just being pedantic - I'll ask a non-science type what they would say. Trouble is, I'll probably have to explain what a hydrofoil is...
     
  12. May 3, 2007 #11

    Danger

    User Avatar
    Gold Member

    Naw, don't put yourself out; I concede the point. I was just explaining my sloppy use of the word. :biggrin:
     
  13. May 3, 2007 #12
    :cool: look, if an objects density(or volume,not sure which.Think it density.) is lower than 1, no matter what it is, it will float. its all about buoyancy:cool:
     
  14. May 3, 2007 #13
    Doesnt it depend on the liquid it is trying to float in. The less dense object will float and the denser will sink, so since a brick is denser than water it sinks, likewise oil poured into water floats because it is less dense. I had always thought that is the main principle behind it. Is this correct?
     
  15. May 4, 2007 #14

    rcgldr

    User Avatar
    Homework Helper

    In the case of the water bug or mosquito, it causes the "skin" of the tension layer of water to displace other water (small depressions in the water). I'm not sure how much of the "floating" for the water bug is due to displaced water and how much to just the surface tension.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: What cause an object to float?
  1. What causes this? (Replies: 1)

Loading...