Coulomb's Law With Three Particles

[GingerBread27]

I know how to use the law with two particles and sometimes with three, but the way this problem is set up has me a bit confused.

Use coulomb's law to find the electric force (magnitude and direction) on q for (a)q=2e-6 C and (b)q=-4e-6C.

The picture is this *sorry I have to actually draw it out*
(3e-6 C)--3cm---(q)---2cm--(4e-6C).

How do I use Coulomb's law to find the force on a particle IN BETWEEN two particles. Also does the fact that q changes from postive to negative (part a and then part b) affect this problem?

 

[MathStudent]

You can use the superposition of forces principle for coulombs law,
That is The net force acting on a particle is the (vector) sum of the forces from the other particles.
This means we can calcualte the force from each particle seperatly and then add these to get the net result ( I'm being very redundant )

Be careful to consider the directions of each force

come back and post your work if you need more help .

-MS

 

[wais]

To use Coulomb's Law with three particles, you will need to calculate the electric force between each pair of particles and then add them together vectorially. In this case, you will need to calculate the force between q and the particle with charge 3e-6 C, and the force between q and the particle with charge 4e-6 C. The direction of each force will depend on the distance between the particles and the sign of their charges.

To find the force on q, we can use the formula F = k(q1q2)/r^2, where k is the Coulomb's constant, q1 and q2 are the charges of the two particles, and r is the distance between them.

For (a)q=2e-6 C, the force between q and the particle with charge 3e-6 C will be repulsive since they both have the same sign. The force between q and the particle with charge 4e-6 C will be attractive since they have opposite signs. To find the total force on q, we can use vector addition to add these two forces together. The magnitude of the total force will be the sum of the individual forces, and the direction will depend on the direction of the individual forces.

For (b)q=-4e-6C, the force between q and the particle with charge 3e-6 C will be attractive since they have opposite signs. The force between q and the particle with charge 4e-6 C will be repulsive since they both have the same sign. Again, we can use vector addition to find the total force on q.

The fact that q changes from positive to negative does affect the problem, as it changes the direction of the forces between q and the other particles. Remember to use the correct signs in your calculations to account for this change.

In summary, to use Coulomb's Law with three particles, calculate the force between each pair of particles and add them together vectorially. The sign of the charge will affect the direction of the force, so make sure to use the correct signs in your calculations.