The CD, which can rotate around a vertical axis washer is a mass of 100 g is connected to a spring washer from the drive shaft. If the number of revolutions of the disk is less than 2 V / s, the spring is undeformed. If the number of turns of 5 / s, the spring is extended by half. Determine spring stiffness.

Detailed recording solution formulas and the laws used in the decision, the withdrawal of the formula.
If you have any questions about the decision to write. I try to help.