# Circle of Cylinders

1. Jul 22, 2008

### Evales

I have an EPW that I don't quite know how to get started.
Below is the EPW question and then after that is what I am stuck with.

There are n identical cylinders glued upright to a board. Each cylinder has a radius of r and that centers of their bases lie on a large cirlce of radius R They are even spaced around the circle. A loop of wire encloses the cylinders.

Find in terms of n, r and R,
1. The length of the loop
2. The area contained by the loop
3. Do these formulae hold when there are two cylinders?

I was wondering how you find the amount of the wire that is around the cylinder. Surely it changes for the number of cylinders, but how? Also for question 2 I will need a way to calculate the angle. My working is below:
Using two cylinders as an example, the circumference of an entire circle in looped with wire is eventually made as it loops around both of the cylinders and connects together, so perhaps the amount of wire touching each cylinder = (circumference of the cylinder)/n but judging from the existance of question 3 I could be wrong, can someone confirm my answer?

By the way, I understand picturing these questions may be hard, try drawing a quick diagram of the two cylinder thing and perhaps 3 cylinders (it helps)

Also, Math Help Forum is not working, does anyone know why?

2. Jul 22, 2008

### Evales

Sorry for posting in the wrong part of the site. I have moved the question