6. a) Use Coulomb's law. b.) net force is vector sum of force on particle one from particle two and force on particle one from particle three. Use trig to find this force (law of sines ?)
7. Assume when spheres touch, charge will transfer until each sphere has identical charge, or one-half of total charge of both spheres. Let original charge be q , write Coulomb's law for original force. Now find fractional part of q remaining on each sphere and write Coulomb's law in terms of new charges.
8. Net force on third charge equals zero, so forces of attraction and repulsion are equal. Force on charge 3 from charge 1 equals - force on charge 3 from charge 2.
9. Draw diagram of charges and distances. Net force = 0, so force on Q from 1st charge = force on Q from 2nd charge.
12. After connection is made, charges are equal; solve for final charge. Total original net charge is twice the final charge. Sum of original charges = original net charge. Write Coulomb's law in terms of one original charge and solve.
13. Third charge must be on a line joining the 2 charges but not between them. Net force = 0, so force on three from one = - force on three from two. If distance to far charge is x, then distance to near charge is 10 - x
16.a) Set gravitational and electrostatic force equal. Look up mass of earth and moon, solve for q. b) Hydrogen ion will have charge and mass of proton.
17.a) Net force on Q = 0, so force from other Q = - total force from q's. b) Net force on q must now be 0, so force from other q = - force from Q's. Can both of these relationships be satisfied?
