Question

A drum brake is shown in the figure. The drum is rotating in an anticlockwise direction. The coefficient of friction between drum and shoe is 0.2. The dimensions shown in the figure are in mm. The braking torque (in Nm) for the brake shoe is

• A. 64

Answer 1

The correct option is A 64

Taking $\sum M_o=0$

$\Rightarrow 1000\times 800=F_t\times 100+R_N\times 480$

$\Rightarrow 8000=F_f+4.8R_N$

$F_f=\mu R_N=0.2R_N$

$\therefore 0.2R_N+4.8R_N=8000$

or $R_N=\frac{8000}{5}=1600N$

$\therefore F_f=\mu R_N=0.2\times 1600$

$=320N$

Braking torque,

$T=F_f\times r=320\times 0.2=64Nm$