Explain why the normal force and the force of gravity acting on a book as it sits on a desk are not Newton’s Third Law of Motion force pairs. in length wording like a 9th grader
The normal force and the force of gravity are not Newton's Third Law of Motion force pairs because they act on different objects. According to Newton's Third Law, when one object applies a force on another object, the second object applies an equal and opposite force on the first object.
In the case of a book sitting on a desk, the force of gravity pulls the book downwards towards the center of the Earth, while the desk exerts an upward force called the normal force to support the weight of the book. Even though these forces have equal magnitudes, they act on different objects - the force of gravity acts on the book, and the normal force acts on the desk.
Since the book and the desk are two separate objects, the normal force and the force of gravity do not fulfill the criteria for a Newton's Third Law force pair. Newton's Third Law force pairs involve forces acting on two different objects and have equal magnitudes but opposite directions.