Answer
$2.9$ feet.
Work Step by Step
The given equation is
$\Rightarrow t=\frac{\sqrt d}{2}$
The hang time was $t=0.85$.
Substitute the value of $t$ into the equation.
$\Rightarrow 0.85=\frac{\sqrt d}{2}$
Multiply both sides by $2$.
$\Rightarrow 2\times 0.85=2\times\frac{\sqrt d}{2}$
Simplify.
$\Rightarrow 1.70=\sqrt d$
Square both sides.
$\Rightarrow (1.70)^2=(\sqrt d)^2$
Simplify.
$\Rightarrow 2.89=d$
Hence, the approximate vertical distance is $2.9$ feet.
