Correct choice is (b) ω2 – ω1/ ωmean
The explanation is: Let N1 = Minimum equilibrium speed,
N2 = Maximum equilibrium speed, and
N = Mean equilibrium speed = N1 + N2 / 2
Sensitiveness of the governor = N1 – N2 / 2
= 2(N1 + N2) / N1 + N2
= ω2 – ω1/ ωmean
where ω1 and ω2 = Minimum and maximum angular speed, and
ωmean = Mean angular speed.