#### Answer

The rider is moving with a speed of 34.3 m/s

#### Work Step by Step

Let the centripetal acceleration $a_c$ be $10~g$.
$a_c = \frac{v^2}{r}$
$10~g = \frac{v^2}{r}$
$v^2 = 10~g~r$
$v = \sqrt{10~g~r}$
$v = \sqrt{(10)(9.80~m/s^2)(12~m)}$
$v = 34.3~m/s$
The rider is moving with a speed of 34.3 m/s.