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