Physics question--finding the magnitude of the electric field


by nba23
Tags: electric, field, magnitude, physics, questionfinding
nba23
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Dec27-08, 04:14 PM
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1. The problem statement, all variables and given/known data
A charged insulating ball of mass 7.0g with a uniform charge of 1.5mC hangs from a light thread inclined at an angle of 8 degrees to the vertical. Calculate the magnitude of the electric field.


2. Relevant equations
q=mg/e

e= Fe/q


3. The attempt at a solution
I tried to use e=mg/q and i kept getting the wrong answer. Im not sure how or if i should use the given angle.Im confused because i dont know which formula i need to use for this question.
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Doc Al
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Dec27-08, 04:57 PM
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Quote Quote by nba23 View Post
I tried to use e=mg/q and i kept getting the wrong answer.
That would apply if the ball were suspended solely by the electric field, but its not--there's a string attached.
Im not sure how or if i should use the given angle.Im confused because i dont know which formula i need to use for this question.
Which way does the field point? (I presume horizontally.)

What forces act on the ball? (Draw a diagram for yourself.) What must the net force be? Hint: Consider vertical and horizontal force components separately.


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