# 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

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.