Force Transmitted Through a Flexible Joint Imagine a length of wood with string fastened to one end of it, lying on a fairly smooth surface (Fig. A). Pull the stick towards the right, by means of the string, from a direction roughly at right angles to the length of the stick. The fi rst thing that happens is that the string pulls taut. Obviously the stick is not going to move whilst the string is slack. The weight of the stick acts as though concentrated at its center of gravity, and so the stick as a whole does not start to move in the direction of the pull until its center of gravity is in line with the string. So the stick rotates until the axis of the stick and the string are in line, and then moves off (Fig. B).