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## Homework Statement

A point charge 'q' hangs motionless from a mass less string at an angle, due to the forces of gravity and electrical attraction with a nearby infinite conducting plane of charge.

Conducting wire sigma = -3.0 E -8 String is next to the conducting wire with a angle

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a. If the mass of 'q' is 4.00 E -6 kg, and it hangs at angle of 25.0 degrees with the vertical, find the charge 'q'.

## Homework Equations

Using the equations, that I learned from mechanics. I broke up the force components in x and y direction.

∑ Fx = Fe - T sin 25º = 0

∑ Fy = T cos 25º - mg = 0

## The Attempt at a Solution

∑ Fy = T cos 25º - mg = 0

T = mg/cos 25º

T = (4.00 E-6 kg) (9.80 m/s^2)/cos (25º) = 3.55 x 10^-5 N (I wrote N on my test and he crossed that out)

Electrical Force = T sin 25º = (3.55 x 10^-5N) sin 25º = 1.50 x 10^-5 N

Now I am lost on how to solve for q. Can you pinpoint where I am making errors and also direct me on how to solve for q? Because on my test I got half of the points.

How would you sketch an electric field diagram of 'q' and 'sigma' ? Also, where would the net electric field be exactly zero?

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