Newton's 3rd Law And Free Body Diagrams

Every force has one and only one 3rd law pair force.

The two forces in each pair act in opposite directions.

The two forces in each pair can act on the same object or on different objects.

The two forces in each pair may have different physical origins (for instance, one of the forces could be due to gravity, and its pair force could be a normal contact force).

The two forces of a 3rd law pair always act on different objects.

Given that two objects interact via some force, the accelerations of these two objects have the same magnitude but opposite directions. (Assume no other forces act on either object.)

According to Newton's 3rd law, the force on the (smaller) moon due to the (larger) earth is

An object is at rest on a tabletop. Earth pulls downward on this object with a force equal in magnitude to mg. If this force serves as the action force, what is the reaction force in the action-reaction pair?

A large truck collides head-on with a small car. The car is severely damaged as a result of the collision. According to Newton's third law, how do the forces acting between the truck and car compare during the collision?

An object is hanging by a string from the ceiling of an elevator. The elevator is moving upward with a constant speed. What is the magnitude of the tension in the string?

An object is hanging by a string from the ceiling of an elevator. The elevator is slowing down while moving upward. What is the magnitude of the tension in the string?