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The weight of a balloon is 'W' when empty and 'Q' when filled with air. Both are weighed in air by the same sensitive spring balance under the same conditions. So using weight due to gravity and buoyant force we find that Q>W as the air inside the balloon is at a greater pressure and hence has greater density than the air outside. So does this mean that a balloon filled with air won't float?

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  • $\begingroup$ What is $P$? Is it the weight of a balloon-sized volume of air at normal atmospheric pressure? Your reasoning seems correct, also. $\endgroup$ – Connor Harris Mar 24 '17 at 14:36
  • $\begingroup$ No, a flat balloon in the first case. $\endgroup$ – Amit Hegde Mar 24 '17 at 14:53
  • $\begingroup$ So $P$ is the same as $W$? $\endgroup$ – Connor Harris Mar 24 '17 at 14:56
  • $\begingroup$ Sorry I don't know how P got there. I will edit the question. $\endgroup$ – Amit Hegde Mar 24 '17 at 14:57
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    $\begingroup$ Think of the balloon as two components. 1) rubber that is denser than the surrounding air, and 2) compressed air that is denser than the surrounding air. Denser things tend to sink to the bottom of less dense things. $\endgroup$ – James Mar 24 '17 at 15:02

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