Hi please help: a solid disk of radius R= 70 cm rotates about its center at an angular speed of 43 revolutions per minute. The mass of the disk is M= 7.7 kg. The moment of inertia of a solid disk is given by 1/2 MR^2. What is the rotational kinetic energy (in Joules) of the disk? Answer with three significant figures

A typical helicopter with four blades rotates at 300 rpm and has a kinetic energy of 2.45  105 J. What is the total moment of inertia, in kg · m2 of the blades?

A horizontal platform in the shape of a circular disk rotates on a frictionless bearing about a vertical axle through the center of the disk.The platform has a mass of 150 kg, a radius of 2.0 m, and a rotational inertia of 300 kgm2 about the axis of rotation.A 60 kg student walks slowly from the rim of the platform toward the center. If the angular speed of the system is 1.5 rad/s when the student starts at the rim, what is the angular speed when she is 0.50 m from the center?

A propeller is modeled as five identical uniform rods extending radially from its axis. The length and mass of each rod are 0.829 m and 2.71 kg, respectively. When the propellor rotates at 589 rpm (revolutions per minute), what is its rotational kinetic energy ??