Question

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

Answer 1

True.

Step-by-step explanation:

This statement is true. According to Netwon's third Law, every force has one and only same and opposite force as reaction.

Actually, the two forces must be originated in two physical points, which act in opposite direction with equal magnitude. The best example of this the force due to gravity and the normal force, which is the unique pair reaction force of the one due gravity.

Therefore, the given statement is true.

Answer 2

Answer: Please see below as the answer is self-explanatory.

Step-by-step explanation:

The Newton's 3rd law, in simple words, explains, that for any force exerted on an object by another one, there exists a reaction from the object acted upon, which consists in another force, that is of equal value that the one is being exerted on it, but in the opposite direction, and is acting on the the other object.

So, Newton's 3rd Law says that for any pair of objects interacting, there is a pair of forces, equal and opposite, that each of them exerts on the other.

It is very important to understand, that in any free body diagram, it must be showed only one of these forces, the reaction that the other object is exerting on the object for which we are drawing the FBD, not the two forces, as the another one is external to the other object.

One example for this is the normal force, the gravity force, etc.