A uniform solid disk is mounted so that it can rotate freely about a fixed
PHYSICS · Multi-part · CBSE · Physics · System of Particles and Rotational Motion · System of Particles and Rotational Motion
Problem
A uniform solid disk is mounted so that it can rotate freely about a fixed, frictionless axle through its center. Points P and Q are painted on the disk at distances rP=4.0cm and rQ=9.0cm, respectively, from the axle. During an experiment the disk is spun up until it reaches a constant angular speed ω that is maintained for several seconds.
Answer the following questions about the motion of points P and Q when the disk is rotating at this constant angular speed.
(a) Describe qualitatively how the linear (tangential) speed of a point on the disk depends on its distance from the axle while ω remains constant.
(b) Rank the magnitudes of the linear speeds of points P and Q. Provide clear justification for your ranking.
(c) Suppose the angular speed of the disk is doubled. Explain how this change affects the linear speeds of points P and Q and whether the ratio vQ/vP changes.
(d) Sketch a graph of linear speed v (vertical axis) versus radial distance r (horizontal axis) for points on the disk while ω is constant. Clearly label the axes and indicate the positions of points P and Q on your graph.