Question

An object is dropped from 39 ft below the tip of the pinnacle atop of 363 ft tall building. The height h of the object after t seconds is h=-16t^2+324. How many seconds pass before reaching the ground

Answer 1

Answer:

4.5 seconds pass before reaching the ground

Step-by-step explanation:

The height of the object is given by the following equation:

$h(t) = -16t^{2} + 324$

How many seconds pass before reaching the ground

It hits the ground when h(t) = 0. So

$h(t) = 0$

$-16t^{2} + 324 = 0$

$16t^{2} = 324$

$t^{2} = \frac{324}{16}$

$t = \pm \sqrt{\frac{324}{16}}$

$t = \pm 4.5$

There are no negative instants of time, so only the positive answer interests to us.

4.5 seconds pass before reaching the ground