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

4.5 seconds pass before reaching the ground

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) = (324)/(16)`

`t = \pm \sqrt{(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