# Circular motion and water whirl

1. Mar 7, 2006

### JDBB

i can picture it in my head, though i can't explain it with physical concepts:

-A pail of water can be whirled in vertical non-uniform circular motion such that at the top, none is spilled. How so?

any help is appreciated

2. Mar 7, 2006

### Andrew Mason

What is the condition for water to spill (think of it in terms of forces)? What are the forces acting on the water? If the pail is being whirled around in a circle so no water moves downward when it is upside down, what does that say about the magnitude of the net downward force acting on the water?

AM

3. Mar 7, 2006

### Harmony

Try to consider the centripetal force, the weight of the pail, and the normal reaction of the pail to water.

4. Mar 8, 2006

### JDBB

At the top of the trajectory both the weight components are completely downwards which is why im having some trouble explaining this...

5. Mar 8, 2006

### Hootenanny

Staff Emeritus
However, there is a normal reaction force acting upwards. Can you write an equation for the normal reaction force at any point in the rotation? (HINT: You will need to use tig).

6. Mar 8, 2006

### Andrew Mason

What is the acceleration of the water at the top? Hint: it is not zero.

AM