If an object is dropped from a $173-$foot$-$high building, its position $($in feet above the ground$)$ is given by $s(t)=-16t^{2}173,$ where $t$ is the time in seconds since it was dropped.

$($a$)$ What is its velocity $1$ second after being dropped?

$($b$)$ When will it hit the ground?

$($c$)$ What is its velocity upon impact?

$($a$)$ The object's velocity $1$ second after being dropped is $$

$($Simplify your answer.$)$