Fluid Mechanics Density problems

  1. Is this correct?

    A 6-kg piece of metal displaces 1 liter of water when submerged. What is its density?
    Density = mass/volume 1 liter of water = 1000 cm3 = 1 kg
    Ans: 6 kg / 1000 cm3 = .006 cm3

    How would this one work out?
    When a 2.0-kg object is suspended in water, it ‘masses’ 1.5 kg. What is the density of the object?
    I'm guessing:
    Density = mass/volume = 2.0 kg/1.5 kg = 1.333
    Or 2.0 kg/ 1500 cm3 = .00133 cm3

    Now I'm totally lost on what to do:

    A vacationer floats lazily in the ocean with 90% of his body below the surface. The density of the ocean water is 1.025 kg/m3. What is the vacationer’s average density?
  2. jcsd
  3. Tide

    Tide 3,143
    Science Advisor
    Homework Helper

    The buoyant force is equal to the weight of the water displaced (Archimedes principle). That allows you to do a force balance from which you can ultimately determine the volume of the swimmer!
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