Question

An object is thrown off of a 25 foot building and the height of the object in feet ismodeled by the function h (t) = -16t2 + 42t + 25, where t is the time in seconds.How long does it take for the object to reach the ground?

Answer 1

We will determine the time it takes the object to reach the ground as follows:

$-16t^2+42t+25=0\Rightarrow t=\frac{-(42)\pm\sqrt[]{42^2-4(-16)(25)}}{2(-16)}$$\Rightarrow\begin{cases}t=-0.5 \\ t=3.125\end{cases}$

From this, we can see that it will take 3.125 seconds to reach the ground. [Since is the only positive value]