Conservation of Angular Momentum
Most recent answer: 10/22/2007
Finally, it stops due friction.
Can we apply the law of conservation of angular momentum in this case ?
Thanks
- Jessie (age 15)
Auckland, New zealand
Mike W.
(published on 10/22/2007)
Follow-Up #1: Formation of Water Vortices in Tanks
- Jeff Moreland (age 66)
Peterborough England
Hi Jeff,
A lot of experiments were done on similar topics many decades ago. Actually, most of these experiments were trying to detect the Coriolis force in water vortices, and in the process they answered your question.
The researchers* found that even if you leave a tank of water for many hours without bumping it, there still remains a bit of net angular momentum from the random motions in the water. When you drain the water, then, the water rotates faster and faster as it nears the plug hole in order to conserve angular momentum. (Actually, there are a few much more complicated theories about how vortexes form around plug holes, but the experimental consensus* agrees with my description above: conservation of angular momentum magnifies the small net rotation left over from when the tank was filled.)
These experiments showed that in order to get rid of this initial net rotation, you would have to let the water sit still for over a day in an isolated, vibration-stabilized and temperature-stabilized environment.
If you take care of these variables (as the experimenters did years ago), you shouldn't observe rotation at the equator, and you could observe the rotation induced by the Coriolis force as you moved away from the equator.
Cheers,
David Schmid
*See Shapiro (1962), Binnie (1964), etc.
(published on 01/10/2014)