Only two forces acts on the traffic light: the tension T of the cable (upward) and the weight of the traffic light (downward). The weight is
[tex]mg=(19 kg)(9.81 m/s^2)=186.39 N[/tex]
If the traffic light is at equilibrium, the resultant of the two forces must be equal to zero (Netwon's second law):
[tex]T-mg=0[/tex]
Therefore the tension of the cable is
[tex]T=mg=186.39 N[/tex]
