# Homework Help: Electrostatic force problem in newtons

1. Apr 21, 2007

### bagwellaj

Three charges are fixed to an xy coordinate system. A charge of +14 uC is on the y axis at y= +3 m. A charge of -14 uC is at the origin. Lastly a charge of +47 is on the x axis at x= +3 m. Determine the magnitude and direction of the net electrostatic force on the charge at x= +3 m. Specify the direction relative to the -x axis.

Magnitude is in Newtons; direction is in degrees.

State whether the direction is above or below the -x axis.

2. Apr 21, 2007

### Päällikkö

3. Apr 21, 2007

### bagwellaj

If tried to get the force between points x any y, and also between x and the origin, by using the formula F= Kq1q1)/r^2. The radius between x and the origin I assumed is 3, and by using the pythagoreon theorem, I used the square root of 18 for the radius between x and y. The force between x and y came out to be .3286 N. The force between x and the origin came out to be -.65727 N. I added them together to get the net electrostatic force, which came out to be -.3287 N. I'm not sure if I did this problem right. The only thing I could think to come up with for the direction is 45 degrees.

4. Apr 21, 2007

### Päällikkö

Force is a vector, and in this case the vectors are not pointing in the same direction. Break the vectors into x and y components.

5. Apr 21, 2007

### bagwellaj

I did cos45= (x/.3286) to get the magnitude of the force between x and y going in the same direction as the force between x and the origin. Does addin them together then give me the correct net force?

6. Apr 21, 2007

### Päällikkö

Supposing I understood what you were about to do: yes, you get the net force in x direction. To get the total net force though, you have to take the y component into account as well.