1. The problem statement, all variables and given/known data The book I am reading says that given a point mass(m) at the point x, the quantity mx is the "moment about the origin)" It then defines the moment of a collection of points as M = m(1)x(1) + m(2)x(2) + .... m(n)x(n) where m(1) = mass of first point and x(1)=distance of first point from origin It then defines that the center of gravity (X) of the point masses is the moment (M) divided by the total mass(m). X=M/m This is all in one dimension,i.e. like the point masses are on a seesaw(x axis) 2. Relevant equations 3. The attempt at a solution Previously I learnt that moment = torque. In one dimension, torque is defined as the force times the distance from the pivot point. hence torque of a point mass from the origin is Fx. if moment= Fx then how can the "moment about the origin" be mx? mass is not a force.