# physics

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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*10-6)*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

• physicshttp://www.jiskha.com/display.cgi?id=1293915742#1293915742.1293916579 -

http://www.jiskha.com/display.cgi?id=1293915742#1293915742.1293916579

• physics -

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".

• physics -

cos 30 = 1/2

so 9*16 /4 and figure out decimal= 36 *10^(9-12+2)

= 3.6

• physics -

oh sorry, cos 30 = .866
so
3.6*.866/.5

6.24

• physics -

thank you. this was very helpful.

• physics -

You are welcome.

• physics -

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?