Question:A circular ring of radius R and mass 9 m is placed on a perfectly smooth horizontal surface. An ant of mass m starts moving along the ring. Select the correct conclusions.(A) Trajectory of centre of ring is a circle of radius (B) Trajectory of ant is also a circle but a radius (C) Ratio of linear speed of centre of ring and that of ant is (D) Ratio of angular speeds about a common fixed point is Answer:In the situation given, as there is no external force and hence centre of mass will remain at rest.

Distance of centre of mass from ant is Distance of com from centre of ring,

As they will be always diametrically opposite and hence they will move in circular trajectories about com.Thus option (A) and (B) are both correct.Now, as their time period will be same.

(D) is correct.

(C) is wrong.Hence A, B and D is correct.