Hello everyone. I understand the concept of work in general, but the concept of negative work still somewhat baffles me. One of my main problems is this: according to my textbook, 3 conditions must be met in order for work to be done, and one of them is "at least part of the force must be in the same direction as the displacement." Well, how can negative work occur if the force in displacement are going in opposite directions? Thanks for the help!