In a band brake, the tension in the band decreases from the value P₁ at the pivot side of the band to P₂ at the lever side. If r is the radius of the drum, then the net torque on the drum is

Explanation:-

Band brakes - 

A flexible band of leather or rope or steel with friction lining is wound around a drum. Frictional torque is generated when tension is applied to the band. It is known that the tensions in the two ends of the band are unequal because of friction and bear the following relationship:

\(\frac{P_1}{P_2}= e^{\muθ}\;\)

where

P₁ = tension in the tight side,

P₂ = tension in the slack side,

μ = coefficient of kinetic friction and

θ = angle of wrap. 

If the band is wound around a drum of radius r, then the braking torque is  

⇒ T = (P₁ - P₂)× r