I am not sure I get the concept of centrifugal force.. If we have a stone tied to a thread and we just spin it in a circle, and while we are spinning it in a circle, the thread breaks and the stone flies off tangentially. If we watch this motion from an inertial frame, which force will be responsible for making the stone fly of tangentially? Since, when seen from an inertial frame, there is no centrifugal force.. Another case could be : An object is placed on a frictionless disk and the disk is rotated about its axis with some velocity. When we see the motion of the object from an inertial frame, we will see that stone first slides to the end of the disk and then flies off tangentially ( right? since there is no friction ) Again, which force will be held responsible for this motion? Could it be centrifugal force? I've learnt that centrifugal force is a pseudo force used to validate Newton's equations when we see the motion of an object from a non- inertial frame. So which force is responsible for this tangential motion?