Recent content by Jamesgortrig

So under no circumstances I subtract work in an energy statement? It's always added?

Well, in the first instant of time when the book is being pushed, there's more energy than the second instant. I'm subtracting because friction is in opposite direction of displacement. With the force pushing the book gone, ∑E2 should have the work subtracted from it, as the friction from the...

Work done on the book by the table (resulting in the friction). So technically external because it's a normal external interaction with the desk

My net energy statements are... ΣE2 = ΣE1 - w In this case, calculating a positive answer badges server right? But I would still consider it to be negative?

Sorry. It should say he pushes a book ALONG a desk.

Homework Statement A student pushes a 0.65kg box Ali g a desk. When he stops pushing the book, it moves 85cm before stoping (slowing down in this period). Coefficient of friction between book and Table is 0.27.Calculate the work done on the book by the friction. Should it be positive or...