Why Does a Lopsided Bottle Fall to the Opposite Side?

[disregardthat]

I just thought of something, imagine this scenario:

You have an empty bottle of sode\water(whatever) and you hold it lopsided, at the point where it theoretically would stand still. But then move the top half a millimeter towards the center, and then release it. Then it will "fall" to the center and then tip over to the other side. In my mind, it should be falling to the excact same place on the other side, (ignoring other forces than cinetic energy's proportion with stationary energy) and then tip back to the originally place and then do this infinite numbers of time. Including other forces, it will fall slightly less to the opposite side each time it "falls".

BUT, the question is: I have released a bottle like how i said, and it fell over on the other side!
The energy that is "gained" from the trip to the center should exceed the energy needed to tip over to the opposite side!

What is this, and why does it happen?

 

[berkeman]

Interesting question. I just did it with an empty plastic bottle, and it settled (did not fall on the far side). I can see how it could tip if there is liquid in the bottle, but it does seem like an empty one should not tip over. Was your bottle really empty?

 

[disregardthat]

I am going to do the experiment here on the table with a 1,5 litre bottle.

It didnt fall over ...

i did the same experiment with a bottle of shampoo. it is a bit left in the bottle. and it is not totally round. then the sides are equal to each other. So it guess the same laws interpret here.
It did fall over. You said you would understand if there was something left? why?

 

[Danger]

I believe that Berkeman was referring to the momentum of the liquid. It could slosh against the far side of the bottle and cause it to continue moving in the same direction.

 

[DaveC426913]

BUT, the question is: I have released a bottle like how i said, and it fell over on the other side!
The energy that is "gained" from the trip to the center should exceed the energy needed to tip over to the opposite side!

There may be other factors at play.

Did the bottle slip on the surface when it was righting (or wronging) itself? I'm not sure how, but it seems to me that would affect the transfer of momentum.

 

[berkeman]

Okay, okay, okay. After digging through the trash and trying countless experiments, and then finally locating an empty 2-litre plastic pop bottle in a co-worker's office, we may have an explanation. There is an odd number of little dents/legs on the bottom of the bottle. If you start with the bottle balanced on two adjacent bumps, then it does not tip over the other side. But if you start out with it balanced on only one dent, it tips over the other side often. So starting out on the top of one dent places the bottle a little higher than when it hits on the far side on two dents, which allows it to tip all the way over. Hah! Physics works after all.

 

[disregardthat]

Hehe, I see. It would be weird if the physical laws stopped to exist every time a bottle was released.

 

[Danger]

Sometimes they seem to after I've released the 12th beer.

 

[disregardthat]

Yeah, and you WISH they would next morning! :)

Not only for the bottle that is...

 

[disregardthat]

Sorry for bringing an old thread up, but I found some new evidence that makes the bottle fall over:

A normal empty glass bottle of cola was tipped over and over again, and it showed that it indeed fell over. We thought it might have something to do with air pressure, but with the cork on, it still fell over.

But I think I might know why: The bottle never fell over the excact opposite direction it was dropped from. It fell about 10 degrees to the side. I think it fell over because it's angular momentum was too high before it was on the opposite side, that the bottom couldn't resist it from falling.

Do you have any other reason? This contradict that an empty bottle can not fall over when dropped with no extra force added.

 

[berkeman]

That sounds plausible. I wonder if you can add some small features to the bottom of the glass bottle to accentuate the effect. Like, put a small rigid bump about 10-20 degrees away from the edge that you are starting balanced on. Then as the bottle starts to tip straight the other way, it will get a little nudge to aim it more at the 10-20 degree point where you see it going over all by itself. Or maybe add two small bumps spaced near the starting edge, so that the bottle takes a much more reliable straight-across trajectory and see if it stops tipping all the way over as much. Interesting problem.

 

[disregardthat]

Yes it is. The cole bottle we used had all small rigid bumps at ca each half millimeter or slightly more, I doubt they gave much heffect on the bottles final position.

If you could make the bump be as you say 10-20 degrees away from the edge, it sound only reasonable that it would not fall straight forward, but only bend making the center of the bottle move, and then make it fall. (I'm no expert...)

Isn't it logical that a straight fall on the opposite side is impossible if the bottle is equilant on both sides? Many twists and turns on the bottle might give the effect of it, but it never gets enough energy to really tip straight over. That is just what I believe.