Answer:
A book weighing 5 N rests on top of a table. A downward force of magnitude 5 N is exerted on the book by the force of <u>gravity</u>.
Do the downward force in Part A and the upward force in Part B constitute a 3rd law pair? Yes
The reaction to the force in Part A is a force of magnitude <u>5 N</u>, exerted on the <u>book</u> by the <u>table</u>. Its direction is <u>upward</u> .
Explanation:
According to Newton's third law of motion, when two bodies interact between them, appear equal forces and opposite senses in each of them.
To understand it better:
Each time a body or object exerts a force on a second body or object, it (the second body) will exert a force of equal magnitude and direction but in the opposite direction on the first.
In the case of the book in the figure, the 5 N force exerted downwards due gravity is equal to the 5 N force exerted upwards by the table (Normal force).