Answer
The ratio of the centripetal acceleration between those 2 points is $2.23$
Work Step by Step
We are given $r_1=6.7m$ and $r_2=3m$ and asked to find $a_1/a_2$
2 different points on a single blade will have different speed, different distance from the center and therefore, different centripetal acceleration. However, their rotation period is always the same.
We know that $$T=\frac{2\pi r}{v}=\frac{2\pi r}{\sqrt{a_cr}}=\frac{2\pi\sqrt r}{\sqrt{a_c}}$$ $$\sqrt{a_c}=\frac{2\pi\sqrt r}{T}$$ $$a_c=\frac{4\pi^2r}{T^2}$$
Using this formula, we have $$\frac{a_1}{a_2}=\frac{\frac{4\pi^2r_1}{T^2}}{\frac{4\pi^2r_2}{T^2}}=\frac{r_1}{r_2}$$ $$\frac{a_1}{a_2}=\frac{6.7}{3}=2.23$$
