what force makes water spin down a drain; will it spin even if no motion in water to start with?

Question

anonymous · Answer

centripetal force.

anonymous · Answer

and water would have to have velocity of some kind for centripetal force to take action.

anonymous · Answer

its the Coriolis effect

anonymous · Answer

^might be right actually

anonymous · Answer

it is right, trust me

anonymous · Answer

well he asked what force.
Coriolis isn't a force.

anonymous · Answer

then that would be gravity, the spinning is the effect

anonymous · Answer

coriolis  is an inertial force

anonymous · Answer

I'm pretty sure the force is centrifugal (not centripetal or coriolis) http://www.spiralwishingwells.com/guide/whirlpools.html

anonymous · Answer

http://abyss.uoregon.edu/~js/glossary/coriolis_effect.html

anonymous · Answer

If there is no initial motion in the water, and the drain is perfectly level then the coriolis effect will determine the rotation of the water. Because the Coriolis Effect is so weak though, almost any outside influence at all can easily disrupt and change the rotation as it begins. This is one of those questions where the Coriolis Effect is the answer in a hypothetical and perfectly executed experiment, but otherwise the wind blowing against the water or the direction you pull the plug out of the drain will determine the direction of rotation.

anonymous · Answer

The Coriolis effect, being so weak, has no effect whatsoever on water draining. Gravity pulling on the water is the main force causing spin.  The air in the drain "wants" to go up to replace the water that "wants" to go down the drain, and the most efficient way to do this is via a vortex. It's just like the elementary school project where you glue two coke bottles together and spin the water in it to make it go into the other bottle faster.

anonymous · Answer

David is correct. What usually accounts for the spin of your flush is the orientation of the water outlet holes in the toilet bowl.
If you mean just any drain in general, then refer to Shepcon. Just about any variable is going to affect the flow of the water.  A slope, and obstacle, a force. But the Coriolis Effect will have a negligibly minimal influence on the rotation of the water.

anonymous · Answer

Actually, it's random (for a tub/sink with no orientation).