1. A 0.12 m radius grinding wheel takes 5.5 sec to speed up from 2.0 rad/sec to 11.0 rad/sec. What is the wheel's average angular acceleration?
2. A solid sphere of mass 4.0 kg and radius 0.12 m is at rest at the top of a ramp inclined 15 degrees. It rolls to the bottom without slipping. The upper end of the ramp is 1.2 m higher that the lower end. Find the sphere's total kinetic energy when it reaches the bottom.
3. The standard kilogram is a platinum-iridium cylinder 39.0 mm in height and 39.0 mm in diameter. What is the density of the material?