Solving for Electric Force: A 15cm Ring, 20uC Charge

[huntingrdr]

Homework Statement

A ring with a 15cm radius and with a uniform charge of 20 micro coulombs is in the yz-plane with the origin at its center. What is the force on a -3 micro coulombs charge on the x-axis at x=5cm?

Homework Equations

E=kQx/(R^2 + x^2)^(3/2)

F=QE

The Attempt at a Solution

I tried to plug in the numbers for the above equations and can't seem to get the right answer. I first solved for E and then multiplied it to Q which is -3*10^(-6) C...correct?
The answer should be -6.83 N, but I can't seem to figure it out.

 

[merryjman]

I got -6.8 N when I used your numbers. Check your math, check your unit conversions for the distances and charges, and make sure you're using the correct Q for the electric field.

 

[huntingrdr]

Ahh...I made a mistake on my calculator. Thanks for the help.