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Aluminum Boats and Buoyancy.

  1. Mar 3, 2008 #1
    [SOLVED] Aluminum Boats and Buoyancy.

    All right, here we go.
    I'm stuck doing a "Lab Practicum" which has this specific task:
    Build a boat out of aluminum foil alone. Find the maximum about of mass it can hold without tearing, capsizing, or just plain submersing into a bucket of water.
    The piece of foil is 30cm by 30cm.

    That last bit of information is probably unnecessary because I already designed the boat. It's the way that I find that mystery mass that's got me hung up.

    Thanks so much for the help.
     
  2. jcsd
  3. Mar 3, 2008 #2

    Doc Al

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    What's the volume of the boat? That should tell you how much water it can displace when it's just about to sink. Archimedes's principle will help you figure out the mass that will almost sink it. (Assuming you can load it up without destroying it.)
     
  4. Mar 3, 2008 #3

    rcgldr

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    Put the boat into water, and slowly fill the boat with measured amounts water to see how much water it takes to sink the boat. This method should allow you to test the boat without damaging the boat. Then calculate the mass of the amount of water it took to sink the boat and subtract a small amount. Then repeat the experiment with this smaller amount of water to confirm it remains floating. What is meant by "almost"? Will it get to the point that you use a calibrated eye dropper to firgure out to the nearest drop or so of water it takes to sink the boat?
     
    Last edited: Mar 3, 2008
  5. Mar 3, 2008 #4
    I have to do this all on calculations alone before I actually conduct the experiment. I only get one shot; apparently this is the "fun" of this kind of lab.
     
  6. Mar 3, 2008 #5

    Doc Al

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    That's what I assumed. If you could just measure it, Jeff's method is the way to go!

    Can you figure out the volume of the boat?
     
  7. Mar 3, 2008 #6
    Unfortunately, I never wrote down the volume of the boat and it's at a different location. The boat's pretty much a rectangular box, so the volume isn't hard to find.
     
  8. Mar 3, 2008 #7
    When I try to solve for the mass, I end up with a negative number. Perhaps I'm not using this principle correctly...
     
  9. Mar 3, 2008 #8

    rcgldr

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    You still need to know the weight and volume of your boat. Given this information, you should be able to caculate based on Archimedes's principle how much water will be diplaced by an empty boat. You can probably assume that air has zero mass in this case as the actual mass of the air versus the mass the boat can carry is extremely small.

    Once you know how much water is displaced by the empty boat via calculations, then subtract that amount of water from the amount of water equivalent to the volume of the boat. This will be the limit at which the boat sinks. Take away a small amount from this to get a close enough value for how much the boat can take without sinking.
     
  10. Mar 4, 2008 #9

    Doc Al

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    Show us exactly what you did to solve for the mass.
     
  11. Mar 4, 2008 #10
    Problem solved as of this morning. Thanks for the assistance; it actually did help after I got all the information in front of me.
     
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