A circular steel platform of radius 1.5 m and negligible thickness is rigidly mounted…
PHYSICS · Multi-part · AP · Physics C: Mechanics · Energy and Momentum of Rotating Systems · Energy and Momentum of Rotating Systems
Problem
A circular steel platform of radius 1.5 m and negligible thickness is rigidly mounted on a nearly friction-less vertical axle through its center. The platform has mass 120 kg and is initially rotating counterclockwise at a constant angular speed of 1.8 rad/s. Three identical wood blocks (A, B, and C), each of mass 4.0 kg, are firmly bolted to the top surface so that they all move together with the platform.
• Block A is fixed at the rim.
• Block B is fixed halfway between the rim and the center.
• Block C is fixed 0.30 m from the center.
Ignore any motion internal to each block; treat every block as a small particle located at its bolt position.
(a) Rank, from largest to smallest, the individual contributions to the magnitude of the total angular momentum of the system (platform plus three blocks) about the axle. Write your ranking using the symbols A, B, C, and P (for the platform). If any tie exists, indicate it explicitly.
(b) Describe the physical reasoning that supports your ranking, making specific reference to the properties on which an object's angular momentum depends.