If a book is resting on a table, Earth exerts a force on the book and the book exerts an equal force on Earth. Is this a Newton's third law pair?

Question

If a book is resting on a table, Earth exerts a force on the book and the book exerts an equal force on Earth. Is this a Newton's third law pair?

There is a normal force and the force of Earth but would this be a Newton's third law pair?

Answer 1

Different people explain the Newton's Third Law differently;

here is my explanation.

Suppose that you separate the universe into two parts, so that they can

no longer effect each other, but you do not want them to notice the absence of the other part.

Then you need to substitute the removed influences with "forces".

And the Third Law say that for each force introduced in one part of the universe,

you need to introduce a force in the other part that is of equal magnitude, but opposite direction.

Example I: A book lying on coffee table.

Possible separation

Part 1: the book

Part 2: everything else

Force pair (i): In Part 1 you need to add a substitute for the gravitation force on the book,

and in Part 2 you need to add the opposite force replacing the gravitational attraction by the book.

Force pair (ii): Also in Part 1 you need to add the normal force replacing the effect of the coffee

table keeping the book in place, and in Part 2 you need to add the opposite force

indenting the coffee table the way the book use to do it.

As long as the coffee table is able to hold the book up, the forces (i) and (ii)

are equal.

Example II: A book is falling to the Earth

Possible separation

Part 1: the book

Part 2: everything else

You have just one pair of forces representing the gravitation attraction -- one acting on the book

and the other acting on the Earth.

In practical applications of the Third Law you are trying to analyze behavior of one object.

That becomes one part of the universe and everything else is the other.