The brake power (B.P.) of the engine is given by (where W = Brake load or dead load in newtons, l = Length of arm in meters, N = Speed of engine in r.p.m., S = Spring balance reading in newtons, D = Diameter of brake drum in meters and d = Diameter of rope in meters)

Answer: Option D

The brake power (B.P.) of the engine is given by
- $$\text{B}\text{.P}\text{.}=\frac{\text{W}l\times 2\pi \text{N}}{60}\text{ watts}$$
- $$\text{B}\text{.P}\text{.}=\frac{\left(\text{W}-\text{S}\right)\pi \text{DN}}{60}\text{ watts}$$
- $$\text{B}\text{.P}\text{.}=\frac{\left(\text{W}-\text{S}\right)\pi \left(\text{D}+\text{d}\right)\text{N}}{60}\text{ watts}$$
Where W = Brake load or dead load in newtons, $$l$$ = Length of arm in meters, N = Speed of engine in r.p.m., S = Spring balance reading in newtons, D = Diameter of brake drum in meters and d = Diameter of rope in meters.