1. The problem statement, all variables and given/known data a uniform rule has a mass of 90g and its centre of mass is at the 50cm mark. the ruler is suspended by a thread at the 70cm mark, balanced by a mass of weight W hanging from the 80cm mark. Calculate the moment of the weight of the ruler about the 70cm mark. What is the moment of weight W about the 70m mark ?? 2. Relevant equations Principles of moment = Sum of Clockwise motion = sum of anti clockwise motion. 3. The attempt at a solution Calculation of moment of weight of ruler above the 70cm mark. sum of anticlockwise moment = sum of clockwise moment Weight of rule x 20 = (0.090)(10) x 10 => weight of rule = 0.45 N => moment of weight of ruler about 70 cm mark = 9 Nm I know that this is the actual solution to the question but can somebody explain why the distance of the anti clockwise moment is 20cm and the distance of the clockwise moment is 10cm ? As far as possible, can somebody give me reasons to derive at this solution ? As for the moment of the weight W about the 70cm mark, can somebody help ?? I dont really understand this well ..