1.forces are mutual.At the same time appear,disappear at the same time.
2 .the nature of interaction must be the same role in
3.action and reaction forces on the two objects,the role can not cancel each other out.
4.force can also be called reaction,just choose the reference
5.Action and reaction for different point not on the same object,so can't together.
Any two objects in nature are attracted to each other,the direction of gravity on their attachment,the size of the gravity of the m1 and m2 to the mass of the object is directly proportional to the product,and they r of the distance between the two inverse proportion.