Question

A student has six textbooks, each with a thickness of 4.0 cm and a weight of 30 N. What is the minimum work the student would have to do to place all the books in a single vertical stack, starting with all the books on the surface of the table?

Answer 1

well, the second book has to be lifted 4cm, the third 8 cm, ...

you are lifting books 2,3,4,5,6,7,8 Book 5 is the average book, so

work= 30*.04*4 Nm