Question

A firecracker shoots up from a hill 145 feet high, with an initial speed of 80 feet per second. Using the formula H(t) = -16t2 + vt + s, approximately how long will it take the firecracker to hit the ground?

13 seconds
11 seconds
Nine seconds
Six seconds

Answer 1

@sleepyjess @amistre64

Answer 2

\[h(t) = -16t^2+vt+s\] we are given the initial speed to be 80 feet/s with a height of 145 feet high, so lets plug that in. \[h(t) = -16t^2+80t+145\] for it to hit the ground we have to solve for h(t) = 0, so we can use the quadratic formula, I leave that to you.\[-16t^2+80t+145=0\] where the quadratic formula is\[ t = \frac{ -b \pm \sqrt{b^2-4ac} }{ 2a }\] as we're solving for time.

Answer 3

Also note you want a positive value.

Answer 4

Thank You

Answer 5

Np :)

Answer 6

Is it D?

Answer 7

Yes, that sounds pretty good to me :)