question_answer

A weight mg is suspended from the middle of a rope whose ends are at same level. If the rope is no longer horizontal, the minimum tension required to completely straighten the rope will be                      

A) \[mg\]     

B) \[\sqrt{mg}\]

C)  Infinite  

D)  zero

Correct Answer: C

Solution :

 The given situation can be shown as from figure \[2T\,\sin \theta =mg\] or \[T=\frac{mg}{2\sin \theta }\] when rope is straight, \[\,\theta ={{0}^{o}}\] \[\therefore \] \[T=\frac{mg}{2\sin \theta }=\infty \]    (infinite)