When an object is not moving all the forces acting on it must sum to zero. The object is said to be in equilibrium. Two cables of different lengths hold a stoplight over an intersection. The force vectors being allied along the two cables are and . The magnitude of each vector is measured in pounds. A third force vector in this situation is the force due to gravity, and is straight downward. How much does the stoplight weigh?

Question

When an object is not moving all the forces acting on it must sum to zero. The object is said to be in equilibrium. Two cables of different lengths hold a stoplight over an intersection. The force vectors being allied along the two cables are <20, 18> and <-20,12>. The magnitude of each vector is measured in pounds. A third force vector in this situation is the force due to gravity, and is straight downward. How much does the stoplight weigh?

anonymous · Answer

30,  18 + 12

perl · Answer

note that the drawing is not drawn to scale.

perl · Answer

|dw:1432326206074:dw|

perl · Answer

Because it is in equilibrum
 ΣF_x= 0 
ΣF_y = 0

-20 + 20 + W_x = 0
W_x = 0

18 + 12 + W_y = 0 
W_y = -30 

so the weight is 30 units of force downward