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?
A Five seconds

B Six seconds

C Seven seconds

D Eight seconds

Answer 1

When the firecracker hits the ground, H(t) = 0.0 = -16t^2 + 90t + 160 Using the quadratic formula,t = (-90 +- sqrt(90^2 - 4(-16)(160))) / 2(-16)t = -1.42 ort = 7.04

The negative time is extraneous. Therefore,t = 7.04 s.

Seven Seconds is your answer!

Answer 2

I did the test and 7 seconds was the right answer hope this helps