Coulomb's Law and electric field

When you rub a plastic rod with fur, the plastic rod becomes negatively charged and the fur becomes positively charged. As a consequence of rubbing the rod with the fur, 

• the rod gains mass and the fur loses mass. 

• the rod and fur both gain mass. 

• the rod and fur both lose mass.C 

• the rod loses mass and the fur gains mass. 

Three point charges lie at the vertices of an equilateral triangle as shown. All three charges have the same magnitude, but charges #1 and #2 are positive (+q) and charge #3 is negative (–q). The net electric force that charges #2 and #3 exert on charge #1 is in

• the +x-direction

• the -x-direction

• +y-direction

• -y-direction

Three point charges lie at the vertices of an equilateral triangle as shown. All three charges have the same magnitude, but charge #1 is positive (+q) and charges #2 and #3 are negative (–q). The net electric force that charges #2 and #3 exert on charge #1 is in

• the +x-direction

• the -x-direction

• the +y-direction

• the -y-direction

Two point charges and a point P lie at the vertices of an equilateral triangle as shown. Both point charges have the same magnitude q but opposite signs. There is nothing at point P. The net electric field that charges #1 and #2 produce at point P is in

• the +x-direction

• the -x-direction

• the +y-direction

• the -y-direction

Two point charges and a point P lie at the vertices of an equilateral triangle as shown. Both point charges have the same negative charge (–q). There is nothing at point P. The net electric field that charges #1 and #2 produce at point P is in

• the +x-direction

• the -x-direction

• the +y-direction

• the -y-direction

Three point charges lie at the vertices of an equilateral triangle as shown. Charges #2 and #3 make up an electric dipole. The net electric force that charge #1 exerts on the dipole is in

• the +x-direction

• the +y-direction

• the -x-direction

• the -y-direction