Final answer:
The work of carrying a book up the stairs involves lifting the book against gravity, and it depends on the height of the shelf and mass of the book, not on the path or time taken. The total work done against gravity is zero when the book is returned to its original position on the shelf.
Step-by-step explanation:
The work involved in carrying a book up the stairs is a concept from physics that refers to the process of applying force to move an object over a distance. In this case, when you lift a book that weighs 20 N a vertical distance of 1 meter up to a shelf, gravity does -20 joules of work on the book because the force of gravity acts in the opposite direction to the motion of the book.
The amount of work done does not depend on the path taken or the time taken to do the work. However, it does depend on the height of the shelf and the mass of the book. The work against gravity can be calculated using the formula work = force × distance. Therefore, lifting a book directly to a shelf does the same amount of work as lifting it any other path, as long as the end height is the same.
Returning the book to its original position on the shelf would involve doing an equal amount of work against gravity as it took to lift it off the shelf if the height is the same. Hence, the total work done against gravity in the entire process would be zero since you've returned the book to its initial height.