Question

1. If the weight is descending freely, determine the tension in the cord both before and after a brake force P – 100 lb is applied. Neglect the thickness of brake.

Answer 1

Taking mass moment inertia

$\sum M_o=I_o\alpha \implies200*2-F_B(3)=80lb$

$and F_B=f_s*N_B=f_s*(4p)$

$A_s=p=100lb\implies F_B=80lb$ and $\alpha =13.33rad ^{-1}$

$\sum f_y=0 \implies F_B+200=T \implies 280lb$

$T_i=F_Be^{t_i*Q}= T_i=80*e^{0.20*Q_1}$

$T_2=80*e^{0.20*Q_2}\\ Q_2=Tan(71.6^0)\\ Q_1=tan(-45^0)\\ \therefore T_1=146lb ; T_2=65.2lb$