question_answer

    A body is moving in a vertical circle of radius r such that the string is just tout at its highest point. The speed of the particle when the string is horizontal is

A)  \[\sqrt{gr}\]                                     

B)  \[\sqrt{2gr}\]

C)  \[\sqrt{3gr}\]                                   

D)  \[\sqrt{5gr}\]

Correct Answer: A

Solution :

                Since, \[{{v}^{2}}={{u}^{2}}-2gh\] \[\therefore \]  \[{{v}^{2}}=5gr-2g(r)\] \[\Rightarrow \]               \[{{v}^{2}}=3gr\] \[\Rightarrow \]               \[v=\sqrt{3gr}\]