1. The circular blade of a power saw has kinetic energy 44 J. If its rotation rate drops to half, what's its new kinetic energy?
2. A revolving door consists of four rectangular glass slabs, with the long end of each attached to a pole that acts as the rotation axis. Each slab is 2.20 m tall by 1.25 m wide and has mass 35.0 kg.
(a) Find the rotational inertia of the entire door.
(b) If it's rotating at one revolution every 9.0 s, what's the door's kinetic energy?
3. A 145-g baseball has radius 3.7 cm. (a) Assuming uniform density, what's its rotational inertia? (b) The ball is pitched at22 m/s with spin rate 20 Hz. Find and compare the ball s translational and rotational kinetic energies.
4. A wheel consists of 20 thin spokes, each with mass 0.055 kg, attached to a rim of mass 4.2 kg and radius 0.75 m. Find its rotational inertia.