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
Verified Correct Answer: D.
Physical Principles & Numerical Solution
For vertical equilibrium, we have
2Ty = 75N
But \(\frac{Ty}{T}\) = \(\frac{adj}{hyp}\) = cos 60º
∴ Ty = T Cos 60º
=> 2Ty = 2Tcos 60º = 75N
2 x T x 0.5 = 75 => T = 75N
∴ Total tension in the rope = 2 T.
= 2 x 75 = 150N
Source: Myschool Past Questions Archive (Record #14330)