A neutron star of mass 2.0 x 103° kg and radius 10 km rotates with a period of 0.02 seconds. What is its rotational kinetic energy (in J)?

A steel disc with a mass of 1.505 kg and a diameter of 8.00 cm is rotating with angular speed 4.75 rad/s. A second, aluminum disc of the same diameter but with mass 527 g and rotating with angular speed -0.07 rad/s is dropped on to the steel disc and both come to a common angular speed. What is this final angular speed?

What is the angular speed in revolutions per minute (rpm) of a 16.9 g CD with a rotational period of 141 seconds? A 0.374 rpm B 0.213 rpm C 0.553 rpm D 0.511 rpm E 0.426 rpm

4. A pottery wheel of radius 20cm and mass M is freely rotating about an axis through its center at 87 rads/s. A blob of very dense clay of mass 5kg is gently placed on the spinning wheel halfway up its radius (i.e. 10cm from the axis of rotation). This causes the rate of rotation of the pottery wheel to drop to 7.8a rads/s. You can treat the pottery wheel as a uniform disk and the blob of clay as a point particle. The moment of inertia of a disk about an axis through its center is given by I = MR. (a) Write down expressions for the angular momentum of the system before and after the blob has been placed on the wheel. (b) Hence, find the mass M of the pottery wheel.