One balloon is inflated with air, the other with hydrogen, the third with carbon dioxide. Which balls will not fly?

Balloons inflated with air and carbon dioxide will not fly up. The weight of the air inside the ball and the weight of the material from which it is made will always be in total more than the weight of the air, because the ball, inflated with air, will not take off.
Well, if you inflate the ball with carbon dioxide, then it will not take off, since its density is greater than the density of air
(P = 1980 kg / m3> p = 1290 kg / m3).

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