Answer
One revolution should take 9.6 seconds.
Work Step by Step
The formula:
$\frac{v^2}{r} = a$
is re-arranged as:
$v = \sqrt{ar}$
We can use this velocity to find the time for one revolution.
$t = \frac{2\pi r}{v} = \frac{2 \pi r}{\sqrt{ar}} = 2\pi \sqrt{\frac{r}{a}} = 2\pi \sqrt{\frac{r}{0.70g}}$
$t = 2\pi \sqrt{\frac{16 ~m}{(0.70)(9.80 ~m/s^2)}} = 9.6 ~s$
Therefore, one revolution should take 9.6 seconds.
