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

Archimedes principle with a completely submerged ball

  1. Jul 14, 2015 #1
    Greetings,
    I have a question about the classic Archimede's principle.
    A ball inflated with air will not sink into water. My understanding is that it will be pushed from all directions by the surrounding water trying to fill the space occupied by the ball. So there will be a pressure downwards formed by the water column above the ball, and there will be pressure upwards from the water below the ball, and obviously on the sides.
    My question is: if a ball is completely submerged there will be a lot of pressure downwards but no or very little pressure upwards, will the ball remain submerged?
    Thanks
    Dasky
     
  2. jcsd
  3. Jul 14, 2015 #2

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    No, your premise is wrong. The pressure is higher at the bottom of the ball (it is deeper and pressure grows linearly with depth).
     
  4. Jul 14, 2015 #3
    Then what about a different container, like a box, resting on the bottom of a pool? the face in contact with the surface of the pool will have no water pushing upwards, so will it remain down?
     
  5. Jul 14, 2015 #4
    The pressure under the ball will be greater because it is deeper.
    By the way, I have noticed that if such a ball is pushed down under water and then released, the upward acceleration cannot exceed -g. This is because water has to fall by gravity into the space vacated in order to create the upthrust.
     
  6. Jul 14, 2015 #5

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    If you can arrange it such that really no water slips in. This is difficult, but a priori possible.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Archimedes principle with a completely submerged ball
  1. Archimedes's principle (Replies: 3)

Loading...