Question

Medal and fan for quick question please help!

A firecracker shoots up from a hill 140 feet high, with an initial speed of 100 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

Seven seconds

Nine seconds

11 seconds

Answer 1

well H(t) = -16t^2 + 100t + 140
then h(t) would equal to 0
0 = -16t^2 + 100t + 140
then solve for t

Answer 2

Thank you so much :)

Answer 3

yw

Answer 4

@FriedRice .. Hey, Im having issues solving for t. i ran it threw www.mathway.com and gives me a weird answer =/

Answer 5

hmmm ok

Answer 6

god. sorry lol i cannot stand math.

Answer 7

well you dont need mathway lol you can just plug in the points into the quadratic equation

Answer 8

\[-b \pm \frac{ \sqrt{b^2 - 4ac} }{ 2a }\]

Answer 9

-16t^2 + 100t + 140
a = -16
b = 100
c = 140

Answer 10

\[-100 \pm \frac{ \sqrt{1000 -4(-16)(140)} }{ 2(-14) }\]

Answer 11

so when i solve that it should then give me the answer?

Answer 12

yeah but you might make a mistake so i'll just tell you the answer
--------> 7.53357 or 7.5

Answer 13

but you should try if you get that answer

Answer 14

okay thank you so much @FriedRice !!!

Answer 15

yw i wish i helped alot