When a body of mass m is in circular motion the in the string is T .And no other force is acting on the mass m.So why mass m does not move in inside

Dear Student ,
It is not that no other forces are acting on the body when it is rotating in a circular motion. The centripetal force is acting on the body which will act in the outward direction and this will balance the tension force thus the mass will not move inside the circle.


Hope this helps you.
Regards