Timeline for What is precisely the reason that a helium balloon ascends?
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| Oct 10, 2016 at 17:24 | comment | added | Steeven | @Marijn Their accelerations are equal, not their speeds necessarily. Only if you drop them at the same time will the speeds at all later moments be equal. You are correct about this happening in vacuum, and as explained in the answer the difference on Earth is simply that there are other forces than gravity. Because the helium atom must push away air molecules in order to fall freely, it does not fall with the same acceleration as in vacuum. In fact the air molecules also try to push away the atoms under them, and because they are heavier, they succeed! And so helium is pushed up. | |
| Oct 10, 2016 at 9:29 | comment | added | Marijn | But isn't a feather and a hamer falling with the same speed on the moon? So it isn't the weigth/mass that causes the speed/attraction because gravity equals to inertia. Only the friction with the air and/or the upward force of the atmosphere is causing the hamer to fall faster. Although there was on the moon a hamer and a feather for the hamer and feather they were in a vacuum. And therefore if you drop one helium atom and one oxygen atom on earth the would fall with the same speed. But why shoudn't they fall with equal speed when there are many of them, that's my point? | |
| Oct 9, 2016 at 21:25 | history | answered | Steeven | CC BY-SA 3.0 |