関連ワード:  force that pulls objects downward    force that pulls objects down    force that pulls objects down towards the center of the earth    force that pulls things down    force that pulls things down to earth    the force that pulls objects down towards earth's surface    the force that pulls objects downwards is called    a force that pulls objects down to earth    the force that pulls objects down to the earth is known as    the force that pulls objects down when it is thrown up is called