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: Buoyancy of Spheres: max mass added without sinking

  1. Dec 10, 2008 #1
    1. The problem statement, all variables and given/known data

    Styrofoam has a density of 300 kg/m3. What is the maximum mass that can hang without sinking from a 40-cm-diameter Styrofoam sphere in water? Assume the volume of the mass is negligible compared to that of the sphere.

    2. Relevant equations

    Volume of sphere: 4/3 π r3

    3. The attempt at a solution

    I tried this:
    mo/3.35 m3=300 kg/m3
    mo=1005 kg

    To find the exact amount of mass added to the Styrofoam sphere to sink in water:
    1005k + m2/3.35 m3=1000 kg/m3

    m2=2345 kg

    This is obviously an obscenely large mass to make Styrofoam sink in water. Any help is appreciated.

  2. jcsd
  3. Dec 10, 2008 #2


    User Avatar
    Homework Helper

    Check the volume of the sphere.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook