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Questions on calculating material needed for lifting object

  1. Sep 23, 2013 #1
    I am trying to make a floating sentry bot ; though, my plan was to use Helium or with a mixture of Ammonia. I want to find the minimum amount of gas in a balloon require to reach the max height the object should float. I know the buoyancy force is Density * Volmin * g : where the maximum potential energy of gravity is W*Hmax. I'm not sure if I am correct, but I would have to equate the Eg = Wgas correct?
  2. jcsd
  3. Sep 24, 2013 #2


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    Staff: Mentor

    For low heights, there is no relevant max height - either the thing will rise, or it will stay on the ground. You probably need some active control to keep it on the same height.

    Right, and all three values are nearly height-independent for the first ~100m. The same is true for the weight of your bot, its weight is either below or above that value.
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