Introduction to Electrostatics -- Positive charges at the corners of a triangle

[molakko]

Homework Statement

Three positive particles of charges 11 μC are located at the corners of an equilateral triangle of side 15.0 cm. Calculate the magnitude and direction of the net force on each particle.

Homework Equations

Coulomb's Law

The Attempt at a Solution

I think, that this is easy task, but I really don't know how to solve this. Please help me guys :P

 

[gneill]

Hi molakko, Welcome to Physics Forums.

You must make some attempt to show what you've tried or at least what you know about the problem before any help can be given. Pick one of the charges and describe the forces acting on it.

 

[molakko]

Hi molakko, Welcome to Physics Forums.

You must make some attempt to show what you've tried or at least what you know about the problem before any help can be given. Pick one of the charges and describe the forces acting on it.

For every charge 2 forces are acting. They are equal and they are same for every charge, because charges are the corners of equilateral triangle and charges have the same value, so we have to calculate magnitude and direction of the net force only for one particle to solve this task.

 

[BvU]

Correct. So what is it that stops you from doing that ? You have found one symmetry that reduces the work by a factor of three.
Pick one of the three particles and calculate the net force on it !

 

[molakko]

Correct. So what is it that stops you from doing that ? You have found one symmetry that reduces the work by a factor of three.
Pick one of the three particles and calculate the net force on it !

I really don't know how to solve that... just help me, please. I need this solution.

 

[BvU]

Coulombs law gives magnitude and direction for the force of particle 1 on 3 and for the force of particle 2 on 3. Add the two vectors and presto !

 

[molakko]

Is that true that magnitude of the force for two particles is equal to 48.4 N, hence magnitude of net force for each particle is equal to 83.831 N? (Assuming that Coulombs const is equal to 9*10⁹)

 

[berkeman]

Is that true that magnitude of the force for two particles is equal to 48.4 N, hence magnitude of net force for each particle is equal to 83.831 N? (Assuming that Coulombs const is equal to 9*10⁹)

No, you need to add the force vectors. Do you know how to do that? Can you post a sketch of the problem showing the force vectors?

 

[BvU]

No -- at least, I get something else. How did you calculate that ?

No, you need to add the force vectors. Do you know how to do that? Can you post a sketch of the problem showing the force vectors?

Small glitch from our good spirit.

molakko: yes, well done. ${q^2\over 4\pi\epsilon_0r^2} =48.4\ N\ \$ and $\ 2\;48.4\;{\tfrac 1 2}\sqrt 3 = 84 \ N$

 

[berkeman]

Oops, thanks BvU!