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### Coulomb's Law and Particle Repulsion

```Date: 09/26/2004 at 16:43:42
From: Carlos
Subject: Calculate the force of repulsion between two electrons

Two electrons are located 0.08 picometers from each other.  Calculate
the force of repulsion between them.  I do not know the equation and
do not know how to do this problem.

```

```
Date: 09/28/2004 at 10:21:00
From: Doctor Ash
Subject: Re: Calculate the force of repulsion between two electrons

Hi Carlos.

In order to solve this problem, you have to use Coulomb's Law:

F = (K*q*q')/(d^2)

where

F   is the force of attraction or repulsion
q   is the charge on the one particle
q'  is the charge on the other particle
d   is the distance between the charged particles
K   is a constant, approximately equal to 9*10^9 (N*m^2/C^2)

Note that it doesn't matter which electron has charge q and which has
charge q', since multiplication is commutative.

The units should be as follows in order to comply with the unit of K:

q and q'   should be measured in C (Coulumbs)
d       should be measured in m (meters)
F       should be measured in N (Newtons)

So, to solve the above question, first convert the units into the
appropriate ones, i.e.,

1 picometers (pm) = 10^-12 m

Then substitute in the equation to find the magnitude of the electric
force between the electrons.

You now have K and d. What are q and q'? The charge on one electron is
constant and is equal to -1.6 x 10^-19 C.  Thus,

q = q' = -1.6 x 10^-19 C

Now you have all the values on the right side, so you can compute the
force.  The force will have a positive value showing that it is a
repulsive force.  (Attractive force is negative by convention).  I
hope this helps, and if you have any further questions, don't hesitate

- Doctor Ash, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
High School Physics/Chemistry

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