# Should the cold drink come out of a free falling bottle with an open lid?

If I hold an open bottle and perform free fall, say sky diving, along with it from, say 10000ft, while I'm holding the bottle vertically upwards should the cold drink come out of the bottle? Kindly ask for any further details you need.

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No. You, your bottle and drink within it, all (regardless of the bottle orientation) move with the same acceleration that amounts to gravitational acceleration.

In case you are standing on the ground, you and bottle are at rest, while drink (neglecting the constrains of the bottle) moves with gravitational acceleration toward your thirsty throat. :)

Edit: While in the free fall, only gravitational force is acting on you, bottle and drink within it (there are no forces acting between the objects) regardless of the bottle orientation. Thus acceleration and velocity of all three is the same, there is no relative velocity between you and the drink.

However if you are standing on the ground, three forces are acting on you: force of the ground, force of the bottle and force of the gravity. The sum of these three forces is zero, so you are at rest. If bottle is turned downwards, there are two forces acting on the bottle: force of your hand and force of gravity and sum of these two forces is zero, so bottle is at rest. However, there is still only one force acting on the drink, force of gravity, so drink is accelerating. Acceleration creates relative velocity and makes the drink moving toward you.

If bottle is however turned upwards, there are two forces acting on the drink, the force of the bottle and the force of gravity and sum of these two forces is zero. The drink is therefore at rest.

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Can you please elaborate on it? Won't force be a factor acting on the scenario? – ikartik90 May 8 '12 at 13:17
Thanks for that. I get it now. :) – ikartik90 May 8 '12 at 13:34
Not at all.. :) – Pygmalion May 8 '12 at 13:40
The two cases are not equivalent. You should blow air from below past the bottle. This creates a wake with lower pressure. Couldn't the water be sucked out? – Bernhard May 8 '12 at 15:20
@Bernhard You mean sucking the drink from bottle with mouth? I did not understand the problem that way, neither it was described so. And even so, how could you suck the drink out of the bottle if it sticks to the upper part of the bottle during free fall? You only suck the air. – Pygmalion May 8 '12 at 15:39

When skydiving, there is two forces applied to you, gravity and air resistance, slowing your acceleration, you accelerate during about 10s, so the first secs your answer is correct. However it becomes irrelevant when gravity and air resistance negate each other, your speed stabilize and it becomes like if you're on the ground, the liquid will stick to the bottom of the bottle, and go downward your throat if you drink (no air resistance in your throat).

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When gravitational force and air resistance cancel each other, any falling body (the human + bottle + fluid) reaches terminal velocity. Objects moving at a constant velocity don't feel any net force and so nothing will push the fluid out of the bottle once you reach terminal velocity. However, if you (say) yank the bottle down suddenly (while its mouth faces up) the fluid will spill out. – Siva Mar 15 '13 at 4:27