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New guy in trouble!

  1. Jun 16, 2005 #1
    Hello all, this is my first post on this forum having read it from time to time when in need of help for my physics :smile:

    So to the point. My phsyics teacher is meeean, he gave us this huge assignment just before the summer break just so that we wouldn't be given the opportunity to slack of :mad: !

    We are to find the best suitable simple (not to extreme) boat form that has the best speed while applying a certain amount of force to it.. I thought the question was kind of vague, but he insisted on us solving it... So we got a tub and some measuring devices, and substance to make boat shapes out of. Sooooo my question is basically, if i have some graphs showing the position vs time of the boat at different drag force and different weights of the boat, how do i find a general equation for the graph? I have tried best fit lines, and arrived at some equations.. but.. argh... I'm just stuck.. completely stuck...sick of school and longing for that long summer break, so my brain doesnt really function that well..
    Any help would be greatly and deeply appreaciated!

    Student in trouble! :eek:
     
    Last edited: Jun 16, 2005
  2. jcsd
  3. Jun 16, 2005 #2
    Drag force is usually in either F = kv or F = kv^2 form.
    You have the graph. The curve will be a straight line, try to find different values for k. V is velocity.
     
  4. Jun 16, 2005 #3

    NateTG

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    Hydrodynamics is a tough topic. People are still working on boat hull design to this day, trying to improve it.

    Two things that you should keep in mind when working things out are:
    Water doesn't like to move rapidly, so the less, and the more slowly you move it, the better you'll end up doing.
    And, the tail end of the boat is just as important as the front end.
     
  5. Jun 16, 2005 #4
    Thanks for the help guys. Been playing around with the different graphs now, and realiced the difference between the 2 hull shapes (i made 2 hull shapes to check if the difference between the 2) wasn't there .. :grumpy: so I'm gonna have to try to perform some tests with boats with other shapes, and which are shaped in the back as well. The really hard part is to be able to calculate why the different shapes travel at different velocities.. ah well, I'm gonna have loads of fun this weekend! :cry:
     
  6. Jun 16, 2005 #5

    NateTG

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    How are you setting up your experiment?

    I would be inclined to try to get constant velocity movement, and measure force. Using constant force is tricky.

    Also, you might want to try deliberately 'stupid' designs to make sure things are working.
     
  7. Jun 17, 2005 #6
    Well dont i get a constant force when i drop a weight? I have connected the weight to a system so that it pulls horizontally on the boat while being dropped, wouldn't that be a constant force?

    And im trying with many shapes now, starting of with a normal box, to see the difference in the shapes compared to the box.. I might be getting somewhere for once :smile:
     
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