Contrast the force of gravity between these pairs of objects: 1-kg mass and a 2-kg mass that are 1 m apart; a 1-kg mass and a 2-kg mass that are 2 m apart; and two 2=kg masses that are 1 m apart. i dont understand.

force of gravitation between two different masses is given by

here in first case we will have

Newton

another case we have

Newton

another case we have

Newton

so the force will be maximum in last case when two 2 kg mass is placed at 1 m distance and minimum force is in second case when 1kg and 2kg mass is placed at 2 m distance

iron would move it is magnetic there is a mag field around the current in the wire