1. Not finding help here? Sign up for a free 30min 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!

PVg- volume weight

  1. Nov 9, 2005 #1
    I have a problem that I can't solve,

    A bathball with the volume 3,0dm^3 is floating on water and has 6,0% of it's volume down in the water.

    a) Count the bathball's mass , Easy : 0,06*3,0= 1,8hg = 0,18 kg

    Now comes the real problem

    b) how much power do you need to use to force the whole bathball down under water?

    Well for this I though i'd use p*v*g /p (where p is water density)
    Water density 1,0 * 10^3 = 1000*0,3m^3*9,82 = 2946 / 1000 = 2,946 N

    Which totaly wrong it should be 28 N how do I solve this?
  2. jcsd
  3. Nov 9, 2005 #2


    User Avatar
    Homework Helper

    Draw a diagram. You should have three forces.

    "p*v*g /p"
    How did you get this?
  4. Nov 9, 2005 #3

    Don't know what you're suggesting please understand I'm no science freak :cry: :cry: :bugeye: :surprised :rofl: :zzz:

    Yeah I have 3 forces gravity is one my power pressing the bathball down is one and the will to go up is the third. But I do not not the force pressing the item down!?
    And how do I get to know that ?
    Give me a formula or something?
  5. Nov 9, 2005 #4


    User Avatar
    Homework Helper

    There isn't much help I can give without solving the problem. Here goes, though:

    Well, the forces should equal zero (for the minimal force).
    [tex]mg + F = \rho _{water} Vg[/tex]
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?