1. The problem statement, all variables and given/known data A rope that is 30° to the horizontal has a tension of 150 N. It is used to pull a 40kg packing crate on a rough sruface through a distance of 6 m. If the crate moves at a constant speed, find the work done by friction. 2. Relevant equations Energy formulas, not kinematic. 3. The attempt at a solution I'm at a loss for what step to take after drawing my F-B-D. I've got it set up, but just brain-farting what next. I've thought over this problem, and I know it's a very simple one, but I just can't comprehend it or something.