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Mass of a block floating over a heterogeneous density bar

  1. Jul 10, 2012 #1
    Hi!! I just wanted to ask something. If i have a block, that is resting on the left side of a bar, and everything is floating on water, how can I calculate the mass (m) of that block?

    (I have the mass of the bar (M) and the volume on the block (V))
  2. jcsd
  3. Jul 10, 2012 #2


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    Science Advisor

    Depends on what you are able to measure.

    If the bar is nice and regular and has a known density then that would help. Suppose, for instance that it is box-shaped.

    If you were then to measure its length, width and height you could compute its volume and, hence, its mass.

    If you were to measure the depth to which the two ends sink into the water then you would be able to compute the volume of water displaced by the bar+block.

    Given the fact that a floating object displaces a quantity of fluid equal to its mass you could then subtract and derive the mass of the block that rests on the bar.
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