# Net Force Exerted by Two Charges on a Third Charge (Coulomb's Law)

• PHYSteve
In summary, the conversation discusses a problem involving Coulomb's law for the magnitude of force between two particles with given charges and distances. The problem asks for the net force exerted by these particles on a third charge placed between them. The attempt at a solution involves finding the distances between the particles and using the formula for Coulomb's law to calculate the forces exerted by each particle. The answer is ultimately deemed incorrect, with the mistake being that the charges were given in nC instead of C.
PHYSteve
This problem has been posted before with different values for each variable and I
did as best I could to complete it similarly. However, when I attempt to input my final
answer I get it wrong every time. I just wanted to see where I am going wrong, thanks.

## Homework Statement

Coulomb's law for the magnitude of the force F between two particles with charges
Q and Q' separated by a distance d is:

|F| = K(|QQ'|)/d2

Consider two point charges located on the x axis:
one charge, q1 = -14.5nC, is located at x1 = -1.745m
the second charge, q2 = 36.5nC, is located at the origin.

What is the net force exerted by these two charges on a third charge
q3 = 45.5nC, placed between q1 and q2 at x3 = -1.085?

Your answer may be positive or negative, depending on the direction of the force

## Homework Equations

K = 1/4$\pi$$\epsilon$0

## The Attempt at a Solution

I found the distance between q1 and q1 to be 0.660m
I found the distance between q3 and q2 to be 1.085m

I began by finding the charge q1 exerts on q3
by:

|F1| = K*[|(-14.5*45.5)|/(0.6602)] = 1.362E13

(At this point in the problem there is a hint section asking for this force, when I submit the answer I calculated I am told it is wrong.)

And then I found the charge q2 exerts on q3 by:

|F2| = K*[|(45.5*36.5)|/(1.0852)] = 1.268E13

(Again, there is a hint section asking for this value, which also tells me it is wrong)

From those two calculated forces I take F1 - F2 to get a final answer, which is ultimately deemed incorrect.

Any help would be appreciated!

Units! The charges are quoted in nC, not C.

Gah! I knew it would be something small. It always is. Thanks!

## 1. What is Coulomb's Law?

Coulomb's Law is a fundamental law of electrostatics that describes the force exerted between two point charges. It states that the force is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them.

## 2. How is the net force exerted by two charges on a third charge calculated?

The net force exerted by two charges on a third charge is calculated by summing up the individual forces that each charge exerts on the third charge. The direction of the net force is determined by the vector summation of the individual forces.

## 3. What is the unit of measurement for the force calculated using Coulomb's Law?

The unit of measurement for force in Coulomb's Law is Newton (N). In the SI system, the unit of measurement for charge is Coulomb (C) and the unit of measurement for distance is meter (m), which results in the unit of force being Newton.

## 4. Can Coulomb's Law be applied to charges of any magnitude and distance?

Yes, Coulomb's Law can be applied to charges of any magnitude and distance. However, it may not be accurate for extremely small distances, such as within the atomic scale, or for extremely large distances, such as within astronomical scales.

## 5. How does the direction of the force change if the charges are of the same or opposite sign?

If the charges are of the same sign, the force between them will be repulsive and the direction of the force will be away from each other. If the charges are of opposite signs, the force between them will be attractive and the direction of the force will be towards each other.

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