The strength of the gravitational field on the Moon is 1.6 N/kg. If a rock on the moon weighs 200 N, how much does the same rock weigh on the earth?
PLZ HELP

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.

there are no atoms

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.