Answer
$2.9$ feet
Work Step by Step
Plug the given time into the formula. Multiply the denominator on both sides, and then square both sides to get the vertical distance.
$t=\frac{\sqrt d}{2}$
$0.85=\frac{\sqrt d}{2}$
$0.85*2=\sqrt d$
$1.7=\sqrt d$
$d\approx2.9$
