# Homework Help: Find the force

1. Jan 30, 2009

### Obama_US

Find the force ....Urgent!!

1. The problem statement, all variables and given/known data[/b]

5 identical 15 microC point charges are located at the center and corners of a square which defined by -1 < x < 1, -1 < y < 1, z = 0.

Find the force on the 5 microC point charge at (0, 0, 5).

How to calculate the distance ? i used the formula F=[(Q1)(Q2)(r-r1)(k)]/[($$\sqrt{r-r1}$$)^3]+...........but i don't know what is the r for the coordinate since it = -1 < x < 1, -1 < y < 1, z = 0.

r=(x,y,z)....Sorry for my English

Last edited: Jan 30, 2009
2. Jan 30, 2009

### LuisVela

Calculate the distances (geometrically) from the 6th particle to the others, then calculate numerically each force and finally add them all.
In general, try first with the distances, then the potential at (x,y,z), and finally the force.

3. Jan 30, 2009

### Gokul43201

Staff Emeritus
Re: How TO Find the force !!!!

Please show how far you got and which point you are stuck at.

Hint: You do not use any kind of integration method for a small number of point charges. Replace your integral with a vector sum.

4. Jan 30, 2009

### Obama_US

Re: How TO Find the force !!!!

this part "defined by -1 < x < 1, -1 < y < 1, z = 0." i cannot understand....the data is in variable...so how should i know what is the distance? cause it possible to be any value such as 0,0.1 and etc

Thanks for helping ...I just wanted to know use what method to solve

Last edited: Jan 30, 2009
5. Jan 30, 2009

### Gokul43201

Staff Emeritus

1. There are 5 point charges.
2. They are located in the (4) corners and (1) center of a square.
3. The square is defined by the region: x in the interval (-1,1), y in the interval (-1,1), z=0

First draw the x-y axes and draw the square that is described above. What are the co-ordinates of the corners and center of this square?

6. Jan 30, 2009

### Obama_US

sorry i really don't get it...the co-ordinates of the center should be (0,0,0) but the corners co-ordinates i not sure cause it got range from -1 to 1....

correct me if i wrong

Thanks for helping again

7. Jan 30, 2009

### Delphi51

The upper left corner is at (-1,1,0).
The upper right corner is at (1,1,0).
The first two numbers are like coordinates on graph paper.

8. Feb 5, 2009

### Obama_US

i already solved this problem...thanks everyone who helping me