# Electric field and an equilateral triangle

1. Jan 15, 2007

### abeltyukov

1. The problem statement, all variables and given/known data

Three 8 cm long rods form an equilateral triangle. Two of the rods are charged to +8 nC, the third to -8 nC. What is the electric field strength at the center of the triangle?

2. Relevant equations

E = 4piKλL

3. The attempt at a solution

I found the radius of the triangle to be 4.2688 cm. I tried doing E = 4(pi)(9 x 10^9)(100 nC/m) (.042688 m) but that seems wrong. Is L not the radius of the triangle?

Thanks!

2. Jan 15, 2007

### turdferguson

Whats the height of the triangle? Divide that by 2

3. Jan 15, 2007

### abeltyukov

I still don't get the right answer when I plug in 0.0472 m for L. Any ideas?

Thanks!

4. Jan 15, 2007

### turdferguson

Thats still not it...start by finding the height

5. Jan 15, 2007

### abeltyukov

The height is 4.72 cm, right? sqrt (8^2 + 4^2). Where do I go from there?

Thanks!

6. Jan 16, 2007

### turdferguson

This is not resolving vectors if thats what youre thinking. The hypotenuse is 8 cm and one of the sides is 4 cm. Then you need to cut that height in half