A machine part has the shape of a solid uniform sphere of mass 210g {\rm g} and diameter 3.50cm {\rm cm} . It is spinning about a frictionless axle through its center, but at one point on its equator it is scraping against metal, resulting in a friction force of 0.0200 N at that point
Q1：Find its angular acceleration. Let the direction the sphere is spinning be the positive sense of rotation
Q2: How long will it take to decrease its rotational speed by 28.0rad/s
UNIVERSITY PHYSICS （20 MARKS）
2013-10-25 5:40 am
回答 (1)
2013-10-25 6:54 am
✔ 最佳答案
1. Moment of inertia of solid sphere= (2/5).(0.21).(0.0175^2) kg.m^2 = 2.57 x 10^-5 kg.m^2
Hence, angular acceleration = 0.02 x 0.0175/2.57x10^-5 rad/s^2 = 13.6 rad/s^2
2. Time taken = 28/13.6 s = 2.06 s
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