JAMB - Physics (2006 - No. 42)
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
100N
1500N
250N
150N
Explanation
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
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