question_answer

A weight w is suspended from the midpoint of a rope, whose ends are at the same level. In order to make the rope perfectly horizontal, the force   applied to each of its ends must be:

A)                 less than w                        

B) equal to w

C)                 equal to 2w                       

D) infinitely large

Correct Answer: D

Solution :

For equilibrium of body \[mg=2T\,\cos \theta \] \[T=\frac{mg}{2cos\theta }\] For the string to be horizontal                 \[\theta \to {{90}^{o}}\] \[\therefore \]  \[T=\frac{mg}{2\cos {{90}^{o}}}\] \[\Rightarrow \]\[T\to \infty \]