1. The problem statement, all variables and given/known data A student has six books, all of them with a 4cm thickness and a weight of 30N. ¿What would be the minimum work to put the books in one pile, if the six books are in a table? Weight: 30N Thickness: 4cm. Gravity: 9.81ms-2 2. Relevant equations Ep=mgh Ec=(mv2)/2 3. The attempt at a solution I found the mass of each book, which is 3.06kg, and converted the thickness to m, 0.04m. After that, i'm lost. :S I don't know how to work it out..