Notices
Results 1 to 4 of 4

Thread: Density and Floating Question

  1. #1 Density and Floating Question 
    Forum Freshman AlphaParticle's Avatar
    Join Date
    Oct 2010
    Location
    Australia
    Posts
    16
    I recently heard on a television program (mythbusters to those who may know it) and heard that you float on water becuase you are less dense that it! Unfourtanetly immediately after i thought, "Hold on, why would being less dense make you float?". And now here i am asking...Why does being less dense than water make you float? (when answering remember i'm 14!!!)


    "An eye for an eye leaves everybody blind."
    - Martin Luther King Jr
    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Freshman
    Join Date
    Apr 2011
    Posts
    42
    This link will give you an excellent answer on a level you should be able to comprehend.
    Ask a scientist - Floating

    the short version:
    When you put something (say a boat) on the water, it 'bends' the shape of the surface of the water. Water in a pond without wind is nice and flat. a boat however seems to be partially in the water and partially floating. In fact the boat is simply pushing the water below itself away.
    The water however will 'resist' being pushed away.

    So on one side (let's call it the top) there is a boat pushing down. On the bottom there is water pushing the boat upwards. The downward force by the boat is dependant on it's mass. If the water resists harder than the object wants to sink, it will stay afloat. If not, it will sink.

    The upward force from the water is based on the 'volume being affected' by the boat.

    The balance that describes this relationship (mass per volume) is called density. The higher the density, the more weight will be pressing down per volume.

    Iron for example has a density of 7.8kg/dm≥. Water has a value of 1 kg/dm≥.
    if iron is on top it will push down harder than water will 'push up'. vice versa the water cannot press down hard enough for the iron to move. thus water will not sink into iron (assuming the iron is liquid).

    ps: I know I've been loose with some terms like sinking and forces but I'm trying to explain it in Leyman's terms. Don't hold it against me.


    Reply With Quote  
     

  4. #3  
    Veracity Vigilante inow's Avatar
    Join Date
    Oct 2009
    Location
    Austin, TX
    Posts
    3,499
    The concept of buoyancy is useful here, too. Look into some explanations of that like on wiki and that might help.
    Reply With Quote  
     

  5. #4  
    Iuvenis ducis Darkhorse's Avatar
    Join Date
    Mar 2011
    Posts
    105
    Just to give you something else to chew on. All water is not equally dense. Extremely salty water like the dead sea is much more dense that regular sea water or fresh water so objects that are put in it float much easier.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •