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A 55-kg runner runs around the edge of a horizontal
Chapter 4, Problem 98P(choose chapter or problem)
A 55-kg runner runs around the edge of a horizontal turntable mounted on a vertical, frictionless axis through its center. The runner’s velocity relative to the earth has magnitude 2.8 m/s. The turntable is rotating in the opposite direction with an angular velocity of magnitude 0.20 rad/s relative to the earth. The radius of the turntable is 3.0 m, and its moment of inertia about the axis of rotation is Find the final angular velocity of the system if the runner comes to rest relative to the turntable. (You can model the runner as a particle.)
Questions & Answers
QUESTION:
A 55-kg runner runs around the edge of a horizontal turntable mounted on a vertical, frictionless axis through its center. The runner’s velocity relative to the earth has magnitude 2.8 m/s. The turntable is rotating in the opposite direction with an angular velocity of magnitude 0.20 rad/s relative to the earth. The radius of the turntable is 3.0 m, and its moment of inertia about the axis of rotation is Find the final angular velocity of the system if the runner comes to rest relative to the turntable. (You can model the runner as a particle.)
ANSWER:Solution 98P This question is based on the concept of angular momentum conservation. We shall have to find the initial and final angular momenta of the system. Given , mass of the runner m = 55 kg r Speed of the runner v = 2.8 r/s Radius of the turntable r = 3.0 m Therefore, angular momentum of the runner, L r m × v r r r L r 55 kg × 2.8 m/s × 3.0 m 2 L r 462 kg.m /s Now, moment of inertia of the turntable I = 80 kg.m 2 t Its angular