Constants Part A A machine part has the shape of a solid uniform sphere of mass

Question

Constants Part A A machine part has the shape of a solid uniform sphere of mass 225 g and diameter 4.50 cm. It is spinning about a frictionless axle through its oenter, but at one point on its equator it is saraping against metal, resulting in a friction force of 0.0200 N at that point. Find its angular acceleration. Let the direction the sphere is spinning be the positive sense of rotation. rad/s2 Submit Request Answer Part B How long will it take to deaease its rotational speed by 19.0 rad/s? Submit Request Answer

Explanation / Answer

given

m = 225 g = 0.225 kg
r = d/2 = 4.5/2 = 2.25 cm = 0.0225 m
F = 0.02 N

A) use, Torque = -I*alfa

F*r = -(2/5)*m*r^2*alfa

F = (-2/5)*m*r*alfa

==> alfa = -5*F/(2*m*r)

= -5*0.02/(2*0.225*0.0225)

= -9.88 rad/s^2

B) we know, alfa = dw/dt

dt = dw/alfa

= -19/(-9.88)

= 1.92 s

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