A ball attached to a weightless thread rotates in a horizontal plane around a vertical axis. Determine how many times the number of revolutions of the ball per unit time and its kinetic energy will increase if the length of the thread is halved, thereby bringing the ball closer to the axis of rotation.

A detailed solution with a brief note of the conditions, formulas and laws used in the solution, the derivation of the calculation formula and the answer.
If you have any questions about the solution, write. I try to help.