Consider the traffic light (mass 15.0 kg) suspended from two wires as shown in Figure 4.22. Find the tension in each wire, neglecting the masses of the wires.

Strategy

The system of interest is the traffic light, and its free-body diagram is shown in Figure 4.22(c). The three forces involved are not parallel, and so they must be projected onto a coordinate system. The most convenient coordinate system has one axis vertical and one horizontal, and the vector projections on it are shown in part (d) of the figure.  There are two unknowns in this problem (T₁ and T₂), so two equations are needed to find them. These two equations come from applying Newton’s second law along the vertical and horizontal axes, noting that the net external force is zero along each axis because acceleration is zero.

Transcribed Image Text:

Just some of the forces are shown here. T₁ T₂ Sketch Mi (a) 30° (b) T₂ 4.45° W