Astudent librarian lifts a 2.2 kg book from the floor to a height of 1.25 m. he carries the book 8.0 m to the stacks and places the book on a shelf that is.35 m above the floor. how much work does he do on the book?
i understand most of it, but i am unsure of what distance to use. ?

Explanation:

The work done on an object is the scalar product between force and displacement. So we can write the work:

In our case F and d are parallels then we have a common product of their magnitudes.

Now, the total work will be the sum these two works:

Work done when the student librarian lifts a 2.2 kg book from the floor to a height of h₁=1.25 m.Work done when he places the book on a shelf that is h₂=0.35 m above the floor.

Let's recall that the force in this problem is just the weight of the book. F=m*g

The first work will be: . F and h1 are parallelsThe second work will be: is negative because the vector force and the vector displacement are anti parallels.

Finally, the total work will be the sum of W₁ and W₂.

I hope it helps you!

You can find results and justify them? you can test your hypothesis

Good moring let me you on this question the answer the electric force  have a good day ; )