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mot
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Homework Statement
Two circular disks, each of area 4.10×10-4 m2, are situated parallel to one another. The distance between them is small compared with their radii. Both disks are uniformly charged; their charges per unit area are σ = 5.00×10-5 C/m2 for one and -σ = -5.00×10-5 C/m2 for the other. Compute the force exerted by one on the other.
Homework Equations
E=σ/ε
F=qE
The Attempt at a Solution
E=σ/ε=5.00×10-5 C/m2/8.85x10-12
=5.649717514x106N/C
Charge on one plate = σ*Area=5.00×10-5 C/m2*4.10×10-4 m2=2.05x108C
F=qE=2.05x108C*5.649717514x106N/C
=0.1158N
I have tried both the positive and negative version of this answer, both are wrong. I have no idea what I'm doing wrong here...the distance between the plates isn't given, so I can't use coulomb's law (but they're not point charges anyways)
Help?