work done by spring forces -- positive or negative I have gotten the sign wrong on every single spring force-related problem. I'm pretty sure I'm working out the problems correctly, but the answer turns out to be negative when I have it positive, or positive when I have it negative. Of course, on other occasions, having the wrong sign throws off the rest of the problem. Once I switch the sign, the problem works out correctly (according to the answers posted in the back of the book), but I have no real understanding of why I'm doing it. I am using the equations given to me in the book, namely F = -kx and W = -1/2kx^2, and I'm not leaving out the negative sign when I work the problems. I think I keep in mind that the force is supposed to be opposite the displacement. So what do I keep doing wrong here? Can someone please give me some practical or conceptual advice to start getting these problems right?