Internal Combustion Engines
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 = Dia. of brake drum in meters, and d = Dia. of rope in meters)

P = (Wl × 2πN)/60 watts
All of these
P = [(W - S) π (D + d) N]/60 watts
P = [(W - S) πDN]/60 watts

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Internal Combustion Engines
The exhaust valve in a four stroke cycle petrol engine

Opens at 50° before bottom dead center and closes at 15° after top dead center
Opens at bottom dead center and closes at top dead center
Opens at 50° after bottom dead center and closes at 15° before top dead center
May open and close anywhere

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