# Homework Help: Circular motion of a bucket

1. Sep 18, 2011

### ama

1. The problem statement, all variables and given/known data
You swing a 6.5 kg bucket of water in a vertical circle of radius 3.6 m.
What speed must the bucket have if it is to complete the circle without spilling any water?
mass=6.5 kg
r= 3.6

2. Relevant equations
ay=(v^(2)/(r))
may= A-N-Mg

3. The attempt at a solution
I know that the force of gravity on the water and the normal force of the bucket on the water both point down. I assume you need to get the centripetal acceleration first. But I do not know what the applied force is and have no way of knowing. What do I do?

2. Sep 18, 2011

### mateomy

What would need to happen for the water to stay in the bucket? (something needs to equal something else)

3. Sep 18, 2011

### ama

the normal force and gravity must equal the applied force. But if that is the case, then ay is 0 and the problem is unsolvable.

4. Sep 18, 2011

### mateomy

You need to use centripetal acceleration (or a reaction against it), and acceleration of gravity for this one.

5. Sep 18, 2011

### ama

at the top of the path, the normal force the bucket exerts on the water is 0. therefore, applied force, which is equal to normal force, is 0. Thus mg=(m)(v2/r) solving for v gets 5.94 m/s.