is initially rotating clockwise at an n, O. The radius of the disk is 50 4 (20 p
ID: 1782818 • Letter: I
Question
is initially rotating clockwise at an n, O. The radius of the disk is 50 4 (20 points) A disk with moment of inertia of Skgm2 is initially rotating angular speed of 15rad/s around the axis of rotatio cm. The disk was brought 20cm from 0, at an angle =60° as shown in the figure. to rest by an external force of 20 N is applied at distance Calculate the net external torque acting on the disk? a. F-20N b. What is the total angular displacement of the disk? c. How much y eon the disk to bring it to rest?Explanation / Answer
a) T = r*F*sin(theta)
= 0.2*20*sin(30)
= 2 N.m
b) wo = 15 rad/s
I = 5 kg.m^2
anguar acceleration, alfa = -T/I
= -2/5
= -0.4 rad/s^2
wf^2 - wo^2 = 2*alfa*theta
==> theta = (wf^2 - wo^2)/(2*alfa)
= (0^2 - 15^2)/(2*(-0.4))
= 281 rad or 44.8 revolutions
c) Workdone = change in kinetic energy
= (1/2)*I*(wf^2 -wo^2)
= (1/2)*5*(0^2 - 15^2)
= -562.5 J
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