- #1
danvazb
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Homework Statement
This may be simple, but I don't seem to get the right answer:
An electric field \vec{E}=100,000\hat\imath\;{\rm N}/{\rm C} causes the 5.0 {\rm g} point charge in the figure (Intro 1 figure) to hang at a 20^\circ angle.
E = 100,000 N/C, point charge weighs 5 g, hangs at 20 deg angle.
Homework Equations
vec{F} = q vec{E}
The Attempt at a Solution
In my model, I have the point charge hanging to the right of the normal at an angle of 20 deg. I draw a line for weight and one for the force on the charge, pointing right, away from the field.
I figure I have to find the component forces perpendicular for the field and write my equation as follows, to indicate equilibrium.
mg sin 20 deg = F sin 20 ,
9.8 m/s^2 (0.05 kg) = F ,
F = .49 N ;
Now I use the other formula to figure q:
E = q F
100,000 N/C = q (.49 N)
q = 4.9 nC
The answer is q = 180 nC
What am I doing wrong?