Posted by EMMA on Friday, July 11, 2014 at 8:03am.
a 100kg street light is supported equally by two ropes. one rope pulls up and to the right 40 degrees above the horizontal; the other pulls up and to the left 40 degrees . what is the tension of the rope?

PHYSICS  Henry, Thursday, July 16, 2015 at 9:06pm
M*g = 100kg * 9.8N./kg = 980 N. = Wt. of
st. light.
T1*Cos(18040) + T2*Cos40 = 980*cos270.
0.766T1 + 0.766T2 = 0.
0.766T2 = 0.766T1.
T1 = T2.
T1*sin(18040) + T2*sin40 = 980*sin270.
0.643T1 + 0.643T2 = 980.
Replace T2 with T1:
0.643T1 + 0.643T1 = 980.
1.286T1 = 980.
T1 = 762 N. = T2. 
PHYSICS  Henry, Thursday, July 16, 2015 at 9:22pm
Or T1 = T2.
T1*sin(18040) + T1*sin40 = 980*sin270.
0.643T1 + 0.643T1 = 980.
1.286T1 = 980.
T1 = 762 N. = T2.