I've never actually used something like this but in the "olden days" to weigh something they put the object on one end of a rod with a axis in the middle and a CW on the other end. (a scale) Then they checked how much the rod tilted to see how heavy the object was. But I don't understand why the rod didn't just swing all the way down? If one of the ends is heavier then why doesn't it swing all the way down? What's stopping after falling 5cm that wasn't there after 1cm? In other words, if you have a rope around a pulley with a weight hanging on each end of the rope and one of the weights is heavier than the other one - won't the heavy one fall all the way down (untill the lighter weight hits the pulley or something)? Why is this different from a scale? Thanks.