• Question: If you filled a bouncy castle with helium and got in it, would you be able to fly?

    Asked by to Edward, Ian, Mathew, Naomi, sakshisharda on 23 Jun 2014. This question was also asked by .
    • Photo: Sakshi Sharda

      Sakshi Sharda answered on 23 Jun 2014:

      Hello jediknight280102

      Cool name 😉
      Well, if one filled bouncy castle with helium and got in it, they would not float unfortunately! This is because though helium is lighter than other components of the air and can float, but it cannot carry of lift such heavy weights. One normal sized helium balloon can only carry about 14 grams. So imagine how many helium balloons we would need to levitate the castle. But besides that, we would not be able to breathe in that castle! If we carry oxygen cylinders, they would have weight and we would need a lot more helium to carry those too!!

    • Photo: Ian Stephenson

      Ian Stephenson answered on 23 Jun 2014:

      Approximating a bit:

      Air has a density of 1.2 kg/m3
      Helium has a density 0.2 kg/m3

      Roughtly speaking that means if we have 1m3 of helium it will be 1Kg lighter than the equivalent air, so would be able to lift 1Kg. (in practise the helium would be under slight pressure, so we’d do a bit worse, but this is close enough)

      If a typical person weighed 64Kg, then you would need 64m3 of helium to lift them. You would need a cube of helium 4mX4mX4m to lift them. While that’s not a big castle, the castle has just the walls filled, we would need the whole volume filled, so it isn’g going to lift you.

      However the castle itself is pretty heavy – say the weight of another person… It turns out that actually that doesn’t mean we need to make the cube much bigger – a 5x5x5 cube is almost twice as big as a 4x4x4 cube (125m3 vs 64m3), so that gets close to lifting us and its own weight.

      Its a lot more helium than would fit in a bouncy castle though.

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