A firecracker shoots up from a hill 160 feet high, with an initial speed of 90 feet per second. Using the formula H(t) = -16t2 + vt + s, approximately how long will it take the firecracker to hit the ground?

Five seconds
Six seconds
Seven seconds
Eight seconds

Question

A firecracker shoots up from a hill 160 feet high, with an initial speed of 90 feet per second. Using the formula H(t) = -16t2 + vt + s, approximately how long will it take the firecracker to hit the ground? 

 Five seconds
 Six seconds
 Seven seconds
 Eight seconds

anonymous · Answer

@iGreen

anonymous · Answer

this formula lost me, but i think its six seconds

igreen · Answer

$H(t) = -16t^2 + vt + s$

Where $v$ is velocity, and $s$ is the starting point.

igreen · Answer

Plug in what we know:

$H(t) = -16t^2 + 90t + 160$

Graph it.

igreen · Answer

There's the graph.

What's 7.045 + 1.42? @SouthernRebel101

anonymous · Answer

8.465

anonymous · Answer

oh ok thank you!

anonymous · Answer

taking a break from test ill be back and tag you in some more if i need the help

anonymous · Answer

@iGreen

igreen · Answer

Yep, so it took about 8 seconds..