A mirror of weight 75N is hung by a cord from a hook on the wall. If the cord makes an angle of 30o with horizontal, the tension in the cord is
-
A.
100N -
B.
1500N -
C.
250N -
D.
150N
Correct Answer: Option D
Explanation
For vertical equilibrium, we have
2Ty = 75N
But Ty/T = adj/hyp = cos 60o
∴ Ty = T Cos 60o
=> 2Ty = 2Tcos 60o = 75N
2 x T x 0.5 = 75 => T = 75N
∴ Total tension in the rope = 2T.
= 2 x 75 = 150N