Q: Two masses m and M hang at the two ends of a string that passes through a smooth tube as shown in the figure. The mass m movies in a circular path which lies in a horizontal plane. The length of the string form m to the top the tube is l and Ɵ is the frequency of revolution of m, so that M remains stationary ?

(a) $\frac{1}{2 \pi} \sqrt{\frac{m l}{M g}}$

(b) $\frac{1}{\pi} \sqrt{\frac{m l}{M g}}$

(c) $\frac{1}{ \pi} \sqrt{\frac{M g}{m l}}$

(d) $\frac{1}{2 \pi} \sqrt{\frac{M g}{m l}}$

Ans: (d)