When you lift a book from the ground to your desk, what kind of work do you do, negative or positive? By lifting the book, what do you change? Does the book gain or lose energy? What kind of energy?
Ascencion means gain in potential energy and descing is the opposite, hence when you lift a book, you apply a positive work." "You lose energy where as book gains energy. Therefore, positive work on book, negative on you."
