Electric Force Calculation with Two Point Charges on Axis - Step by Step Guide

[gotpink74]

HELP I don't understand at all

Homework Statement

Two positive point charges on the y-axis, each of which has a charge of 5.0 10-9 C, are located at y = +0.60 m and y = -0.60 m. Find the magnitude and direction of the resultant electric force acting on a charge of 7.6 10-9 C located at x = 0.80 m on the x-axis.

Homework Equations

dont know

The Attempt at a Solution

I have tired to many ways with to many numbers.
My teacher hasn't taught these!

 

[SammyS]

Homework Statement

Two positive point charges on the y-axis, each of which has a charge of 5.0 10-9 C, are located at y = +0.60 m and y = -0.60 m. Find the magnitude and direction of the resultant electric force acting on a charge of 7.6 10-9 C located at x = 0.80 m on the x-axis.

Homework Equations

don't know

The Attempt at a Solution

I have tired to many ways with to many numbers.
My teacher hasn't taught these!

Some teachers are like that, however, a few of my students said the same thing about me.

Find the force on the 7.6 nC charge due to each of the other charges, individually.

 

[gotpink74]

so I do 7.6e-9*9e9/70^2

 

[gotpink74]

Homework Statement

Two positive point charges on the y-axis, each of which has a charge of 5.0 10-9 C, are located at y = +0.60 m and y = -0.60 m. Find the magnitude and direction of the resultant electric force acting on a charge of 7.6 10-9 C located at x = 0.80 m on the x-axis.

Homework Equations

F=kq1q2/r^2

The Attempt at a Solution

I don't even know where to start my teacher hasn't taught us this. I have tried to do a vector diagram but it didn't work.

 

[berkeman]

Homework Statement

Two positive point charges on the y-axis, each of which has a charge of 5.0 10-9 C, are located at y = +0.60 m and y = -0.60 m. Find the magnitude and direction of the resultant electric force acting on a charge of 7.6 10-9 C located at x = 0.80 m on the x-axis.

Homework Equations

F=kq1q2/r^2

The Attempt at a Solution

I don't even know where to start my teacher hasn't taught us this. I have tried to do a vector diagram but it didn't work.

Can you show us your diagram? You will get two force vectors acting on the 3rd charge, and the net force is just the componen-wise sum of those forces...

 

[gotpink74]

I attached my picture down below from their I do not know where to go

 

[berkeman]

I attached my picture down below from their I do not know where to go

Good start. Now draw the two force vectors -- one each from the charges on the y-axis. You draw the force vector arrows at the test charge, pointed along the line between the charges. So for the force on the test charge from the top y-axis charge, you draw the force vector at the test charge along the extended line between those two charges. Whether you draw the force vector arrow pointing back up at the top charge, or pointing away down and right, depends on whether the force is attractive or repulsive. Opposite charges attract, right?

Then once you have the two force vector arrows at the right test charge, divide them up into their x & y components, add components, and then combine those two final components to get the total force vector.

 

[gotpink74]

what are X Y components?

 

[berkeman]

what are X Y components?

Seriously? You are doing a problem that involves vectors. Vectors are added component-wise.

http://en.wikipedia.org/wiki/Vector_components#Vector_components

.

 

[gotpink74]

is the x y (40,70)

is this how you find the magnitude

 

[berkeman]

is the x y (40,70)

is this how you find the magnitude

Actually I now notice that your diagram does not match the problem definition. The problem definition mentions y= +/- 0.60m and x = 0.80m. Where did your 40 and 70 numbers come from in your diagram?

Once you get the dimensions right on the figure, draw your two force vector arrows, and use basic trig to get the x and y components of each vector. Then add the components to get the components of the total resultant force.

 

[gotpink74]

is the hypotenuse 100

 

[SammyS]

so I do 7.6e-9*9e9/70^2

Where does the 70 come from?

What is Coulomb's Law for electric force?

 

[gotpink74]

Do I do √0.60^2+0.80^2

 

[gotpink74]

does anyone know how to do this

 

[gotpink74]

Im just trying to get the most help I can

 

[SammyS]

Do I do √0.60^2+0.80^2

Certainly this quantity is involved in this problem.

\displaystyle\sqrt{0.60^2+0.80^2} is the distance (in meters) from the 7.6 nC charge to either of the 5 nC charges.​

What is the force on the 7.6 nC charge due to the charge at y = +0.60 m ?