physics
posted by ali .
Three spheres, each with a negative chrge of 4.0x10^6C, are fixed at the vertices of an equilateral triangle whose sides are 0.20 m long. Calculate the magnitude and direction of the net electric force on each spehere.
i used this: (K)Cos30((4.0*106)*2)/(0.2*2)
and i get 3.1 every time...

I have answered this one twice as well
^ means exponent
times 2 for two spheres forcing third 
http://www.jiskha.com/display.cgi?id=1293915742#1293915742.1293916579

thank you for responding:
i did:
(9.0*10^9)cos30((4.0*10^6)^2)/(0.2^2)
using this i got 3.1. so then i need to double it because it's two spheres. right?
and sorry about the formula in the question. i confused my self with the "times" and "exponent". 
cos 30 = 1/2
so 9*16 /4 and figure out decimal= 36 *10^(912+2)
= 3.6 
oh sorry, cos 30 = .866
so
3.6*.866/.5
6.24 
thank you. this was very helpful.

You are welcome.

Im working on this same question too and i cant figure out how you got the .5 when doing 3.6*.866/.5 ??? because i know the answer is correct, is it because the net force goes through the middle?