a 70.0 cm, uniform, 60.0 n shelf is supported horizontally by two vertical wires attached to the sloping ceiling (figure 1). a very small 25.0 n tool is placed on the shelf midway between the points where the wires are attached to it.a 70.0 cm, uniform, 60.0 n shelf is supported horizontally by two vertical wires attached to the sloping ceiling (figure 1). a very small 25.0 n tool is placed on the shelf midway between the points where the wires are attached to it.