Question

[9.06] 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?

5 seconds

7 seconds

9 seconds

11 seconds

Answer 1

do you know derivatives?

Answer 2

X/ um... i have no clue what that is

Answer 3

t = 7s?

Answer 4

aye ill try anything right now

Answer 5

H(t) = -140 because the stone is goin down from the initiial point, so its negative
vt = initial velocity * time
s = inital displacement = 0

so plug the values in the equation

h(t) = -16t^2+vt + s
-140 = -16t^2 + 100t + 0
u will end up with a quadratic

so solve it

Answer 6

thanks

Answer 7

no probs