question_answer

On the centre of a frictionless table a small hole is made, through which a weightless string of length \[2l\] is inserted. On the two ends of the string two balls of the same mass m are attached. Arrangement is made in such a way that half of the string is on the table top and half is hanging below. The ball on the table top is made to move in a circular path with a constant speed v. What is the centripetal acceleration of the moving ball?

A)  \[mvl\]             

B)  \[g\]

C)  zero              

D) \[2\,mvl\]

Correct Answer: B

Solution :

 Let the tension in each string be T. Then, for the string hanging below the table \[T=mg\] ... (i) For the string on the table top \[T=m{{a}_{c}}\], .... (ii) From Eqs. (i) and (ii), we get \[{{a}_{c}}=g\]