20. Go Multiple-Concept Example 7 deals with the concepts that are important in this problem. A penny is placed at the outer edge of a disk (radius = 0.150 m) that rotates about an axis perpendicular to the plane of the disk at its center. The period of the rotation is 1.80 s. Find the minimum coefficient of friction necessary to allow the penny to rotate along with the disk.

Current Attempt in Progress Multiple-Concept Example 7 deals with the concepts that are important in this problem. A penny is placed at the outer edge of a disk (radius= 0.118 m) that rotates about an axis perpendicular to the plane of the disk at its center. The period of the rotation is 1.71 s. Find the minimum coefficient of friction necessary to allow the penny to rotate along with the disk. Hs = Number i esc eTextbook and Media GO Tutorial Save for Later F1 F2 Units 80 F3 V F4 F5 F6 Attempts: 1 of 5 used AA F7 Submit Answer 5 F8 2 F9 M L Q Nu Un

A small 0.400-kg object moves on a frictionless horizontal table in a circular path of radius 3.30 m. The angular speed is 6.63 rad/s. The object is attached to a string of negligible mass that passes through a small hole in the table at the center of the circle. Someone under the table begins to pull the string downward to make the circle smaller. If the string will tolerate a tension of no more than 113N, what is the radius of the smallest possible circle on which the object can move?

A 33.2 kg boy and a 22.0 kg girl are standing at the edge of a 161 kg merry-go-round of radius 1.41 m that is currently rotating at 32.0 rpm. The two kids then walk inward toward the center of the merry-go-round; while the boy reaches the center, the girl stops halfway. Given their new positions, what is the new rate of rotation of the merry-go-round (in rpm)? For simplicity's sake, you may treat the kids as point masses and the merry-go-round as a flat disk. Hint: Figure 10.12 in the textbook provides a good refresher on the various moments of inertia!