Storm in a bottle

Classical Mechanics Level 1

The contraption shown above forms an airtight seal between two soda bottles, allowing water from one to flow into the other. The flow can start in one of two ways:

Flip the system over at $t=0$ and let gravity pull the water down.
Flip the system over at $t=0$ , and give the system a slight twirl, forming a vortex. The center of a vortex is an empty hole through which air can pass.

Which of the two flows will let the water reach the bottom first?

Twirling the system to form a vortex. Letting gravity do all the work. Same amount of time.

5 solutions

Rohit Ner
Jun 6, 2015

Twirling the system after flipping would decrease the turbulence of water at the junction of the bottles and give it somewhat a streamline flow. Also a continuous passage would be available for air to come up which will not be possible if we just flip the system.

I tried this experiment in person and my result that gravity was faster at getting all the water to drain. A vortex made most of the water drain faster, but the inertia from the rotation left the last centimeter of water spinning fast enough that overall, the vortex took longer to drain

Elchanan Haas - 6 years ago

Try it for bottles with small openings.

Rohit Ner - 6 years ago

Raj Magesh
Jun 7, 2015

Creating the vortex allows water in the upper bottle to displace the air in the lower bottle by giving a way for the air in the lower bottle to escape.

Basically, this experiment proves that air occupies space, and so the water must displace the existing air in order to occupy its space. The air has to have somewhere to go, in this case, the upper bottle!

A somewhat related but cool comic: xkcd

Enjoy the read!

great script ;)

Tootie Frootie - 6 years ago

Anson Tai
Jun 16, 2015

Just think of what people do when their sink is stuck!!

Mariano PerezdelaCruz
Jun 6, 2015

Indeed even if we do not have the inferior bottle air once the pressure inside the bottle plus the height of the water level equalizes the atmospheric pressure, the flow became intermittent a bubble of air get into the bottle and until doesn't reach the surface no water will flow out and when it happens will be like a bubble of water out and the cycle repeat.

Satvik Choudhary
Jun 6, 2015

Its also a common observation that a driink in a bottle comes out least when the bottle nearly full with the reason supposedly be that the place of the drink is taken by vacuum which creates suction pressure. I think that we can apply the same logic in this situatuon.

Storm in a bottle

5 solutions

0 pending reports