A cylinder is rotating about an axis that passes through the center of each circ
ID: 1491175 • Letter: A
Question
A cylinder is rotating about an axis that passes through the center of each circular end piece. The cylinder has a radius of 0.0700 m, an angular speed of 88.0 rad/s, and a moment of inertia of 0.850 kg · m2. A brake shoe presses against the surface of the cylinder and applies a tangential frictional force to it. The frictional force reduces the angular speed of the cylinder by a factor of two during a time of 4.40 s.
(a) Find the magnitude of the angular deceleration of the cylinder.
rad/s2
(b) Find the magnitude of the force of friction applied by the brake shoe.
N
Explanation / Answer
given
w1 = 88 rad/s
w2 = 88/2 = 44 rad/s
I = 0.85 kg.m^2
t = 4.4 s
r = 0.07 m
a) angular acceleration, alfa = (w2 - w1)/t
= (44 - 88)/4.4
= -10 rad/s^2
b) Apply, Torqe = I*|alfa|
F*r*sin(90) = I*alfa
==> F = I*alfa/r
= 0.85*10/0.07
= 121.4 N
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