Electric Forces; Coloumb's Law question

[fyzikschik]

Homework Statement

three spheres, each with a negative charge of 4.0 X 10^-6 C, are at the vertices of an equilateral triangle whose sides are 0.20m long. Calculate the magnitude and direction of the net electric force on each sphere.

Homework Equations

Fe= kq1q2/r^2, where k is the constant, k=9.0 X 10^9 N*m^2/C^2

The Attempt at a Solution

i plugged in the values..but I don't seem to be getting the answer. There are 2 forces acting on each of the spheres, right? the answer is 6.2N

 

[OlderDan]

Saying "I plugged in" is not telling us what you did. Yes there are two forces acting on each charge. How are they acting? How did you combine them?

 

[fyzikschik]

since Fe=kq1q2/r^2
Fe= k*(4.0 X 10^-6C)^2/ (0.20m)^2
Fe= 3.6N


how are they acting? they are supposed to repel each other, but i don't understand how that would affect the magnitude of the force. To combine them, i think i have to add 3.6N + 3.6N..but that isn't working. What do you think?

 

[OlderDan]

since Fe=kq1q2/r^2
Fe= k*(4.0 X 10^-6C)^2/ (0.20m)^2
Fe= 3.6N


how are they acting? they are supposed to repel each other, but i don't understand how that would affect the magnitude of the force. To combine them, i think i have to add 3.6N + 3.6N..but that isn't working. What do you think?

I think you need to remember that forces are vectors and need to be added as directional quantities. I did not check your numerical calculation, but I expect the vector addition is your problem.