You can't have it both ways with the " instantaneous " change of velocity . . . any real force, such as a rocket propulsion system, would operate on a conservation of momentum principle.
2.
Depending on the apparatus the bit is attached to, the performer can alternately swing in circles around the ring below or spin wildly in place, controlling speed by alternately extending her arms and legs out or bringing them in close to her body to speed up ( known as the conservation of angular momentum principle ).
मोबाइल