Question

A short shoe external drum brake is shown in the figure. The diameter of the brake drum is 500 mm.The dimensions a=1000 mm, b= 500 mm and c= 200 mm. The coefficient of friction between the drum and the shoe is 0.35. The force applied on the lever F = 100 N as shown in the figure. The drum is rotating anticlockwise. The braking torque on the drum is (round off to two decimal places).

• A. 20.35

Answer 1

The correct option is A 20.35

By considering the moment about point 'O'

$F\times a=N\times b-\mu N\times c$

$100\times 1000=N\times 500-0.35N\times 200$

$N=232.558$ Newton

Braking torque $=\mu N\times \frac{D}{2}$

$=0.35\times 232.558\times \frac{500}{2}\times {10}^{-3}$

$=20.35Nm$