PhySP18SS6.7.21: THT6B.14 It’s fine if you just want to think of phi as the reference angle, but just so you know it is actually the obtuse angle that extends from the LOA all the way around to radial pointer vector. This has to be the case because Torque has to be negative for this situation since it is causing clockwise motion. All clockwise rotation is negative. So . . . since torque = |r| |F| sin (phi) phi must be in the 3rd or fourth quadrant for sin (phi) to be negative. If that didn’t make sense, don’t worry, it’s too late in the year to worry about it.