# Force and charges homework

1. Sep 8, 2005

### gmuniz

need help to set up problem?
partA:
suppose all the electrons in a quantity of carbon atoms with a mass m were located at the North Pole of the earth and all the protons at the south pole.
what would be the total force of attraction exerted on each grup of charges by the other? The atomic number of carbon is 6, and the atomic mass of carbon isMc. use E0 for the permittivity of free space, e for the magnitude of the charge on an electron,NA for avagadro,s #' and Re for the radius of the earth.
partB:
What would be the magnitude of the force exerted by the charges in part (a) on a third charge that is equal to the charge at the south pole, and located at a point on the surface of the earth at the equator?
part c:
what would be the direction of this force?

2. Sep 9, 2005

### HallsofIvy

Staff Emeritus
Okay, how many electrons would there be at the north pole and what is their charge? How many protons would there be at the south pole and what is their charge? Now, you know, or can look up, the distance from the north pole to the south pole so that should be all the information you need.

Pretty much the same thing except now you have just the one charge (electron or proton?) and want to calculate the force from the north pole and then the force from the south pole. I will give you this much: the net force will be directed north to south (or south to north depending on whether or not the "test" charge is positive or negative).

3. Sep 9, 2005

### H_man

If you imagine that they are separated by the diameter of the earth but otherwise in free space then it is not too hard a question. It would be similar to working out the attractive forces between any two charges in space.

But... with the earth in between??? I am guessing the earth will function as dielectric reducing the field between the two sets of charges. And so it would become quite a complex problem. :uhh:

But remove the Earth and all is good. :rofl:

$$F = \frac {k q_1 q_2 } {r^2}$$