A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk at its center. Rotating flywheels provide a means for storing energy in the form of rotational kinetic energy and are being considered as a possible alternative to batteries in electric cars. The gasoline burned in a233-mile trip in a typical midsize car produces about4.00x 109J of energy. How fast would a49.1-kg flywheel with a radius of0.428m have to rotate to store this much energy? Give your answer in rev/min.

A helicopter has two blades (see figure), each of which has a mass of230kg and can be approximated as a thin rod of length 6.7 m. The blades are rotating at an angular speed of51rad/s.(a)What is the total moment of inertia of the two blades about the axis of rotation?(a)Determine the rotational kinetic energy of the spinning blades.

A thin rod has a length of0.513m and rotates in a circle on a frictionless tabletop. The axis is perpendicular to the length of the rod at one of its ends. The rod has an angular velocity of0.216rad/s and a moment of inertia of1.25x 10-3kgm2. A bug standing on the axis decides to crawl out to the other end of the rod. When the bug (whose mass is 5 x 10-3kg) gets where it's going, what is the change in the angular velocity of the rod?

A solid disk rotates in the horizontal plane at an angular velocity of0.081rad/s with respect to an axis perpendicular to the disk at its center. The moment of inertia of the disk is0.099kgm2. From above, sand is dropped straight down onto this rotating disk, so that a thin uniform ring of sand is formed at a distance0.28m from the axis. The sand in the ring has a mass of0.32kg. After all the sand is in place, what is the angular velocity of the disk?

Conceptual Example 14 provides useful background for this problem. A playground carousel is free to rotate about its center on frictionless bearings, and air resistance is negligible. The carousel itself (without riders) has a moment of inertia of105kgm2. When one person is standing at a distance of1.41m from the center, the carousel has an angular velocity of0.531rad/s. However, as this person moves inward to a point located0.697m from the center, the angular velocity increases to0.725rad/s. What is the person's mass?