question_answer

A simple pendulum of length t and mass m is initially at its lowest position. It is given the minimum horizontal speed necessary to move in a circular path about the point of suspension. The tension in the string at the lowest position of the bob is-

A) 3mg                             

B) 4mg

C) 5 mg                

D) 6 mg

Correct Answer: D

Solution :

To complete the circle \[{{v}_{\min }}=\sqrt{5g\ell }\] \[T-mg=\frac{m{{v}^{2}}}{\ell };\] \[T\,\,-\,\,mg\,\,=\,\,5\,mg\] \[T\,\,=\,\,6\,mg\]