A falling stone takes 0.30 s to travel past a window 2.2 m tall. From what height above the top of the window did the stone fall?

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.