Electric Force Question and Spheres

[delongk]

Three identically charged spheres A, B, and C, each with a charge of +3.0 * 10-7 C, are located at the corners of a triangle whose sides are 30 cm long and all the angles are 60 deg. What is the net force acting on sphere A?

I figured the X coordinates cancel each other out. For the Y:

kqAqB/r^2 cos 30 + kqAqC/r^2 cos 30

since all charges and sides are equal:
2(kq^2/r^2) cos 30

the answer I get is 1.56 *10^-2 but the website says that is not correct. Does anyone know what I am doing wrong??

 

[Andrew Mason]

Three identically charged spheres A, B, and C, each with a charge of +3.0 * 10-7 C, are located at the corners of a triangle whose sides are 30 cm long and all the angles are 60 deg. What is the net force acting on sphere A?

I figured the X coordinates cancel each other out. For the Y:

kqAqB/r^2 cos 30 + kqAqC/r^2 cos 30

since all charges and sides are equal:
2(kq^2/r^2) cos 30

the answer I get is 1.56 *10^-2 but the website says that is not correct. Does anyone know what I am doing wrong??

Perhaps it is a problem with significant figures. Try 1.6 x 10^-2. Your method is correct.

AM

 

[nrqed]

Perhaps it is a problem with significant figures. Try 1.6 x 10^-2. Your method is correct.

AM

I concur with Andrew. Since they gave the charge and length with two sig figs, they probably want you to give 1.6 x10^(-2) N.