- #1

- 53

- 0

## Homework Statement

Four charges of [itex]2*10^-7[/itex] are placed on the corners of one face of a cube of 15 cm. A charge of [itex]-2 * 10^-7[/itex] C is placed at the center of the cube. What is the force on the charge at the center of the cube?

## Homework Equations

[itex] F = k q_1*q_2/r^2 [/itex]

## The Attempt at a Solution

[/B]

I understand how to get the correct answer. Depending upon where we place the charges on one of the cubes faces the forces will be in the direction normal to that face. (sides = y-components, back-faces = x, bottom/top = z-components) and everything else will cancel. So the force will be in the direction of the unit vector [itex]\hat{r} = 1\sqrt 3 <1, 1, 1>[/itex]. This is the part I don't understand, the unit vector's magnitude must be one so makes sense that 3(1/3) = 1 trivially. But, how is the unit vector here giving the force in said direction(s)? Having some trouble with the [itex]\hat{r}[/itex] notation as it is typically left out in most elementary problems.

Last edited: