Refer to the figure below. Find the magnitude of the electric field if the string with a 7 gram ball carrying a charge of 4 x 10-9 C forms an angle of 35o with the vertical.
a. 1.41 x 106 N/C
b. 1.20 x 107 N/C
c. 2.30 x 107 N/C
d. 6.25 x 108 N/C
The Attempt at a Solution
Force due to electric field=Force due to gravity:
which is not an answer...the correct answer in the key is b, but I dont know why?