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Mass, volume, density

  1. Aug 23, 2004 #1
    I am stuck on this question. Can someone please help me!

    Not all objects have a volume that is measured easily. If you were to determine the mass, volume, and density fo your your textbook, a container of milk, and an air-filled balloon, how would you do this?

    Any help would be great. Thanks
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  2. jcsd
  3. Aug 23, 2004 #2


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    Fill a large container to the brim with water, submerse your object completely while capturing all water that overflows. Now weigh the captured water... There is your volume for arbitrary shaped objects. (1 cc water weighs 1 g)

    Edit: Opps this won't work for your balloon.
  4. Aug 23, 2004 #3
    Several two step methods will work for balloon, but I cant think of a single step method.
  5. Aug 23, 2004 #4
    If you don't want to destroy your textbook, vacuum-seal it in a plastic wrapping before submerging. Then remove the wrapping, measure its volume and weight alone, and substract. Or just use a ruler for a good enough approximation.

    Why would the submerging not work with the balloon?
  6. Aug 23, 2004 #5
    Using plastic wrap as you suggest isn't a good idea as it would trap air, and you would get results of the books volume along with some air spaces.

    It won't work with the baloon because the air will compress and change in volume the farther under the water it gets. Same for the air trapped in the plastic wrapped book too...
  7. Aug 24, 2004 #6
    Are you allowed to use a sensitive balance to weigh the 3 objects?
  8. Aug 24, 2004 #7
    I said "vacuum-seal", meaning that the air is sucked out before you seal, like with a pack of hot-dogs, or perhaps a lamb chop.

    If you stay on the surface, you should get a good approximation. Get a container with the same diameter as the balloon. If there is only a cm of water above the balloon, it won't shrink enough to make a difference. Or do one half of the balloon at a time. Or use better rubber. A basketball won't shrink as much.
  9. Aug 24, 2004 #8
    Perhaps alcohol or oil would be better than water to submerge something in, it is lighter.
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