$\rightarrow S_1 = 1095.3\ N$

$\rightarrow S_2 = 1557.6\ N$

$\rightarrow$ $S = \frac{S_2 – S_1}{h} = 232\ N/mm$

$\rightarrow$ $sensitiveness = \frac{N_2 – N_1}{N_{mean}} = \frac{ Range \ of \ speed}{Mean \ speed}$

$= \frac{312\ – \ 285.09}{300}$

$= 0.089 = 8.9$%

For isochronous:

$\rightarrow$ $Fc_1 = mr_1 w^2 \rightarrow$ (mean)

$= 4 \times 0.128 \times 31.41^2$

$Fc_1 = 505.13 \ N$

$Fc_2 = mr_2 m^2 \rightarrow$ (mean)

$= 4 \times 0.152 \times 31.41^2$

$Fc_2 = 599.84\ N$

Put $Fc_1$ and $Fc_2$ in both moment equation from FBD.

$S_1 = 1212.312$

$S_2 = 1439.6$

$S = \frac{S_2 – S_1}{h} = 11.35$