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.
According to Newton's Third Law of Motion, for every action, there is an equal and opposite reaction. However, the normal force and the force of gravity acting on a book on a desk are not Newton's Third Law force pairs because they act on different objects.
The force of gravity is the downward force exerted by the Earth on the book. It is the force that pulls the book towards the center of the Earth. This force exists due to the presence of mass and gravity between the Earth and the book.
On the other hand, the normal force is the upward force exerted by the desk on the book. It is a reactive force that acts perpendicular to the surface of contact between the book and the desk. The normal force prevents the book from sinking into the desk and balances out the force of gravity.
While the force of gravity and the normal force are equal in magnitude and opposite in direction, they act on different objects. The force of gravity acts on the book, while the normal force acts on the desk. Therefore, they do not form a Newton's Third Law force pair.