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holtvg
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Homework Statement
A 3.10 kg, 31.0-cm-diameter disk in the figure is spinning at 300 rpm, how much force must a brake apply that is perpendicular to the rim of the disk to bring the disc to a halt in 2.4 s.
Homework Equations
t=i*alpha wf=0+alpha*t t=fr*sin(theta)
The Attempt at a Solution
i=1/2mr^2=.24
wf=0+alpha*t wf=0 w0=300 rpm=31.4 rad/s t=2.4 s alpha=-13.1 rad/s^2
t=i*alpha=-3.1 n*m
t=fr*sin(theta) theta=90 degress
t=fr
-3.1=f*.155 r=15.5 cm=.155 m
f=-20 n
Don't know what I'm doing wrong but it's not the correct answer.
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