A disc weighing 1 kg, radius 0.2 m, rotates at a frequency of 100 rpm. What work must be done to stop

A disc weighing 1 kg, radius 0.2 m, rotates at a frequency of 100 rpm. What work must be done to stop the rotating disc?

Initial data: m (mass of a rotating disk) = 1 kg; R (radius of the disc) = 0.2 m; ν (disk rotation speed) = 100 rpm.

The work that must be done to stop the disk will be equal to the change in its kinetic energy of rotation: A = ΔEk = J * ω ^ 2/2, where J (moment of inertia of the rotating disk) = m * R2; ω (angular velocity of rotation of the disk) = 2 * Π * ν.

The formula for calculations will take the form: A = m * R ^ 2 * 2 * Π * ν / 2 = m * R ^ 2 * Π * ν.

Let’s perform the calculation: A = 1 * 0.2 ^ 2 * 3.14 * 100 = 12.56 J.