# Homework Help: HELP HELP HELP spheres!

1. Oct 27, 2004

### maxx

HELP HELP HELP!! spheres!

Consider a solid sphere of radius R containing a total charge Q which is uniformly distributed throughout the volume with a volume charge density rho.

a) find the total force exerted by the electrostatic field on the charge in the 'northern hemisphere'. express your answer in terms of the total charge Q and the radius R of the sphere

b) evaluate your answer to part a) using R=1m containing 10kg of electrons

c) find the repulsive force between two sperical volumes of radius R=1m, each containing 10kg of electrons held fixed and separated by a distance of 3000km

d) by what factor does the magnitude of the repulsive electro. force, found in part c) exceed the gravitational attractive force of the two masses

e) if the forces holding the two spherical volumes of electrons, fixed at a distance of 3000km, were to vanish, find the initial acceleration that would be experienced by the two 10kg masses. express your answer of units of g-forces of 9.81m per second squared.

2. Oct 27, 2004

### chroot

Staff Emeritus

- Warren

3. Oct 27, 2004

### maxx

a) E(r)=1/4Pi(epsilon)*Q/R^2 r^

i don't know how to get the force after the electric field..i used gauss law

4. Oct 27, 2004

### maxx

i also thought about using tensor analysis but i have to use a lower level approach instead..integrating the maxwell tensor is fine..but i can't use it here..