Question

A pebble falls off a cliff at a height of

256 ft. If the equation for height as a
function of time is
h(t)=-16t2+ initial height where t is time
in seconds and h(t) is height in feet, how
many seconds will it take for the pebble
to hit the ground?

Answer 1

Check the picture below.

so the pebble will hit the ground when h(t) = 0.

It's noteworthy that the pebble is falliing off a cliff, so it was at rest, so its initial velocity is 0, so in essence is falling as fast as gravity can drop it.

`~~~~~~\textit{initial velocity in feet} \\\\ h(t) = -16t^2+v_ot+h_o \quad \begin{cases} v_o=\textit{initial velocity}&0\\ \qquad \textit{of the object}\\ h_o=\textit{initial height}&256\\ \qquad \textit{of the object}\\ h=\textit{object's height}&\\ \qquad \textit{at`