Circular motion of water in a glass

1. Sep 18, 2008

mavrick3987

Hey all,

I'm attempting a lab where I want to have water moving in circular motion in a glass. I realized that the water will climb the side of the glass creating a sort of conical shape, if you will. I know that there is a way to calculate the change in height that occurs as the speed of the water increases. I was thinking centrifugal force, but I don't remember my motion well enough for this sort of thing.

Any and all help would be freakin' awesome

Aveld

2. Sep 18, 2008

HallsofIvy

Staff Emeritus
The centripetal force necessary to hold something in a circle of radius R with constant speed v (and so angular speed $\omega$ is mv2/R or $m\omega^2R$. That vector force, <-mv2/R,0>, added to the gravitational force <0, -mg> gives total force m<-v2/R, -g>, in the xz-plane. More generally, it is [itex]m<-(v^2/R)cos(\theta), -(v^2/R)sin(\theta), -g>. It is the "equilibrium" condition, that that vector be perpendicular to the surface of the water that determines its form.

3. Mar 11, 2011

ashishsinghal

As I recall, It forms a paraboloid

4. Mar 11, 2011

Andy Resnick

Are you rotating the glass, or are you moving the glass in orbital motion- moving the glass in a circle without rotating the glass? There's a big difference.