Vectors are confusing me. I'm not sure if I'm doing it right

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The discussion revolves around calculating the electric field and force at a specific point due to two fixed charges. The user initially struggles with vector addition and determining the correct magnitudes for the electric fields generated by each charge. They eventually find the magnitudes of the electric fields, E1 and E2, but seek clarification on how to break these into x and y components. The recommended approach is to use trigonometric functions to resolve the vectors and apply the formula E = Kq/r² for accurate calculations. The conversation emphasizes the importance of correctly converting the vectors into components to solve the problem effectively.
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Homework Statement


Charge q1 = +8.36 μC is fixed at the origin and charge q2 = -4.28μC is fixed on the +x-axis, 0.371m from the origin.

(a) Find the direction and magnitude of the electric field at a point P that has coordinates (0.466, 0.466) m.

(b) Find the direction and magnitude of the force on a -2.00 μC charge placed at the point P. (Please state the direction as an angle measured counterclockwise from the positive x-axis.)

Homework Equations


E = Kq/r^2

The Attempt at a Solution



Find θ1 = atan(0.466/0.466) = 45 degrees
θ2 = atan(0.466/0.095) = 78.48 degrees

I figured you just add the two vectors. For some reason I don't know how to... What is confusing me is that a can't use -4.28μC, for example, as the actual value. I think I need to use E=kq/r2 Here's what the diagram looks like

I really appreciate any helpEDIT:

I got the first part. It is attached
Would the second part just be F=Eq?

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You should review this as its important.

Bascially convert the two vectors into components along the x and y-axis and go from there.
 
jedishrfu said:
You should review this as its important.

Bascially convert the two vectors into components along the x and y-axis and go from there.
But what values should I be using?
 
josh12399 said:

Homework Statement


Charge q1 = +8.36 μC is fixed at the origin and charge q2 = -4.28μC is fixed on the +x-axis, 0.371m from the origin.

(a) Find the direction and magnitude of the electric field at a point P that has coordinates (0.466, 0.466) m.

(b) Find the direction and magnitude of the force on a -2.00 μC charge placed at the point P. (Please state the direction as an angle measured counterclockwise from the positive x-axis.)

Homework Equations


E = Kq/r^2

The Attempt at a Solution



Find θ1 = atan(0.466/0.466) = 45 degrees
θ2 = atan(0.466/0.095) = 78.48 degrees

I figured you just add the two vectors. For some reason I don't know how to... What is confusing me is that a can't use -4.28μC, for example, as the actual value. I think I need to use E=kq/r2 Here's what the diagram looks like

I really appreciate any help
[/B]
Hello josh12399 . Welcome to PF .

upload_2016-7-17_20-51-58.png


The resultant you have for E1 + E2 looks to be correct providing that you used correct magnitudes for E1 and E2. (You have placed the vectors in a rather unusual position relative to point P.)

What did you get for the magnitudes of E1 and E2 ?
 
SammyS said:
Hello josh12399 . Welcome to PF .

View attachment 103390

The resultant you have for E1 + E2 looks to be correct providing that you used correct magnitudes for E1 and E2. (You have placed the vectors in a rather unusual position relative to point P.)

What did you get for the magnitudes of E1 and E2 ?

To be honest I have no idea what to use for the magnitude. I tried a bunch of different things and got totally different answers.

I thought of splitting them up into EX1, EY1, EX2 and EY2, but I don't know what the actual magnitude should be. Should it be (k*q*cosθ)/r2 for the x and (k*q*sinθ)/r2 for the y?
 
josh12399 said:
To be honest I have no idea what to use for the magnitude. I tried a bunch of different things and got totally different answers.

I thought of splitting them up into EX1, EY1, EX2 and EY2, but I don't know what the actual magnitude should be. Should it be (k*q*cosθ)/r2 for the x and (k*q*sinθ)/r2 for the y?
Use the following:
josh12399 said:
E = Kq/r2
for the electric field (magnitude) due to each charge.
 
SammyS said:
Use the following:

for the electric field (magnitude) due to each charge.
For each component (x and y)? Or should I just use the pythagorean theorem to find the diagonal distance from the charge to P?
 
josh12399 said:
For each component (x and y)? Or should I just use the Pythagorean theorem to find the diagonal distance from the charge to P?
... just use the Pythagorean theorem to find the diagonal distance from the charge to P
 
SammyS said:
... just use the Pythagorean theorem to find the diagonal distance from the charge to P

E1 = 1.730*105 N/C
E2 = -1.701*105 N/C

Now I take the X and Y components using sine and cosine?
 
  • #10
josh12399 said:
E1 = 1.730*105 N/C
E2 = -1.701*105 N/C

Now I take the X and Y components using sine and cosine?
Yes.
 
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