# [Electrical force] Electrical charge in equilateral triangle

• sea333
In summary, the conversation is about calculating the sum of two forces on a third charge using the Pythagorean theorem or the rule of cosines. The person is unsure about the use of angles and the other person suggests using the Law of Cosines.

#### sea333

Homework Statement
In each corner of equilateral triangle there is a charge with 5 nAs. What force works on the e3 charge (see image). Length of a side is 5 cm. e1 is charged with negative charge.
Relevant Equations
F = (1/(4*Pi*eps0))*(e*e)/r^2

Not being a computer myself, I find that a bit hard to follow! Can you explain what you're doing?

F23 is a force on the 3rd charge from 2nd charge
F13 is a force on the 3rd charge from the 1st charge
Fr is a sum of both (Pythagorean theorem).

sea333 said:
F23 is a force on the 3rd charge from 2nd charge
F13 is a force on the 3rd charge from the 1st charge
Fr is a sum of both (Pythagorean theorem).
Doesn't Pythagoras only apply to right-angled triangles?

sea333
PeroK said:
Doesn't Pythagoras only apply to right-angled triangles?
I will check if forces are right-angled

sea333 said:
I will check this
There is a generalisation called the "rule of cosines", which is very useful.

PeroK said:
There is a generalisation called the "rule of cosines", which is very useful.
I have used Cosines to calculate Fr and I still don't get the correct result:

#### Attachments

• Capture4.PNG
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That's not right! Did you look up the rule of cosines?

sea333
Should I use the Law of cosines ? c^{2}=a^{2}+b^{2}-2ab*cos
Then I would need angle gamma?
I have updated the picture

Yes. ##\gamma## can only be one thing!

I have used for gamma = 60 and got correct result but how do you know that gamma = 60 ?
I don't know why I thought that any of the angles is 90 degrees.
The correct result:

If you want to use Pythagorean theorem or Cos/Sin function you need one angle to be 90 degrees.

sea333 said:
how do you know that gamma = 60 ?

## What is an electrical force?

An electrical force is a type of physical force that is caused by the interaction of electrically charged particles. It can be attractive or repulsive, depending on the charge of the particles involved.

## What is an electrical charge?

An electrical charge is a fundamental property of matter that determines how it will interact with other charged particles. It can be positive or negative, and is measured in units of coulombs.

## What is an equilateral triangle?

An equilateral triangle is a type of triangle in which all three sides are equal in length. It also has three equal angles of 60 degrees each.

## How does electrical charge behave in an equilateral triangle?

In an equilateral triangle, the electrical charge is distributed evenly among the three sides and angles. This means that the electric field is also evenly distributed throughout the triangle.

## What is the relationship between electrical force and electrical charge in an equilateral triangle?

The electrical force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. In an equilateral triangle, the distance between charges is equal, so the force will depend solely on the magnitude of the charges.