mfb said:Anything that looks like a bottle is probably to unstable to keep vertical long enough.
I'm sure a finite-element analysis can give some approximation, and I'm also quite sure that there is no analytic solution to the problem. In a purely theoretical situation, the bottle will get slower and slower without fully stopping.
A bottle can spin on the surface of the water due to the principle of angular momentum. When the bottle is set in motion by a person's hand, the water molecules around it also start to move and create a circular motion. This motion creates a force that keeps the bottle spinning.
The circular motion of the bottle is due to the surface tension of the water. This surface tension creates a force that acts perpendicular to the surface of the water, causing the bottle to rotate in a circular motion instead of moving in a straight line.
The speed at which the bottle spins on the water is affected by several factors, including the initial force applied to the bottle, the surface tension of the water, and the shape and weight distribution of the bottle. A larger force, lower surface tension, and a more balanced bottle will result in a faster spin.
No, the bottle cannot spin indefinitely on the surface of the water. Eventually, the energy from the initial force applied to the bottle will dissipate, causing the bottle to slow down and eventually stop spinning. The surface tension of the water also plays a role in how long the bottle can spin, as it can break at a certain point, causing the bottle to stop spinning.
To make the bottle spin faster on the surface of the water, you can increase the initial force applied to the bottle, decrease the surface tension of the water by adding a surfactant, or use a more streamlined and evenly weighted bottle. However, be careful not to apply too much force or decrease the surface tension too much, as this can cause the bottle to spin out of control or sink into the water.