GATE 2019 ME (ME1) – Question 54
The shown single-block short-shoe brake has torque capacity 250 N·m. Its cylindrical drum rotates anticlockwise at 100 rpm; friction coefficient is 0.25. Find dimension a (mm), to one decimal place, such that maximum actuating force P is 2000 N.
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Correct answer: 212 to 213
Explanation
Lever moment balance gives $2.5aP=Na+\mu N(a/4)$. Thus $N=2.5(2000)/(1+0.25/4)=4705.882$ N. Since $T=\mu Na$, $a=250/[0.25(4705.882)]=0.2125$ m, or **212.5 mm**.