# Physics problem involving tension and electric fields

Two small spheres, each of mass 4.00 g, are suspended by light strings 10.0 cm in length. A uniform electric field is applied in the x direction. The spheres have charges equal to -2.00 multiplied by 10^-8 C and +2.00 multiplied by 10^-8 C. Determine the electric field that enables the spheres to be in equilibrium at an angle of θ = 15.0°.

Here is a link to the image:
http://img.photobucket.com/albums/v720/lackofrespect/p23-62.gif [Broken]

m1 = 4.00g
m2 = 4.00g
θ = 15.0°

I thought I might use E = (k|q||q|)/r²

I'm confused about the charges on the two spheres. How are they apart if they have opposite charges? Shouldn't it be that only like charges can repel and be in equilibrium?

Any help would be great to get me started.Thank you.

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welcome to pf!

hi aaronmilk3! welcome to pf!
I'm confused about the charges on the two spheres. How are they apart if they have opposite charges? Shouldn't it be that only like charges can repel and be in equilibrium?

Any help would be great to get me started.Thank you.
hmm … that is odd!

i'll guess that the static electric force is so small that it can be ignored …

does that work?

This is a problem from Web Assign which is a web site you are assigned homework through. I'm wondering if there is an error and both charges should have been positive.