Answer
The riders move through a distance of $16.8~m$
Work Step by Step
We can convert the angle to radians:
$120^{\circ}\times \frac{\pi~rad}{180^{\circ}} = \frac{2\pi}{3}~rad$
We can find the distance through which the riders move:
$d = \theta~r$
$d = (\frac{2\pi}{3}~rad)(8.0~m)$
$d = 16.8~m$
The riders move through a distance of $16.8~m$
