question_answer

A uniform disc of radius R and mass m is connected to a wall by string of length 2R. The normal reaction of wall is

A)  mg                                        

B)  mg/2

C)  \[\text{mg/}\sqrt{\text{3}}\]                   

D)  2mg

Correct Answer: C

Solution :

 \[mg=T\cos {{30}^{o}}\]               \[N=T\sin {{30}^{o}}\] \[\Rightarrow N=\frac{mg}{\sqrt{3}}\]