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?

Answer 1

13 seconds
11 seconds
Nine seconds
Six seconds

Answer 2

what I got so far is there...80
-16t^2+145t+

Answer 3

@NetflixAndNo

Answer 4

@rachethoes55

Answer 5

@Anaise

Answer 6

@ThatGuyAvery

Answer 7

@ParthKohli

Answer 8

@AloneS

Answer 9

@peterg2001

Answer 10

http://openstudy.com/study#/updates/4f588bb9e4b0c9fd2d4bcb8b

Answer 11

http://openstudy.com/study#/updates/520927a6e4b01dd6868af15f

Answer 12

http://openstudy.com/study#/updates/520927a6e4b01dd6868af15f

Answer 13

thanks @peterg2001

Answer 14

last one (D six seconds)

Answer 15

i thought it was 6 just wasnt sure...

Answer 16

v initial = 80

s initial = 145

H(t) = 0 (because we want to know when the height is back on the ground)

0 = −16t^2 + 80t + 145
quadratic formula
t = 1/4 ( 10+- 7sqrt(5)) = -1.413 or 6.413
t = 6 seconds to get down


x^2+3x-18=0
(x+6)(x-3)=0
x=-6,3

Answer 17

Hope this helps