Question

A block brake is shown in the figure below.the diameter of brake drum is 200 mm, as mean co-efficient of friction is 0.25. For actuating force of 500 N, the braking torque in N-m is ,

• A. 4.5 Nm
• B. 18.5 Nm
• C. 45 Nm
• D. 15.6 Nm

Answer 1

The correct option is D 15.6 Nm

$\sum M_{pivot}=0$

$\therefore P\times 500=R_N\times 200$

$\Rightarrow 500\times 500=R_N\times 200\Rightarrow R_N=1250N$

$\text{Friction force}=\mu R_N=0.25\times 1250=312.5N$

$\text{Torque 'T'}=312.5\times \frac{100\times {10}^{-3}}{2}=15.625Nm$