Question

A firecracker shoots up from a hill 165 feet high with an initial speed of 110 feet per second. Using the formula H(t) = −16t2 + vt + s, determine how long it will take the firecracker to hit the ground.
7.2 seconds
7.5 seconds
7.8 seconds
8.1 seconds

Answer 1

But firecrackers just explode...they don't fly into the sky...Bottlerockets fly in the sky! :-)

Answer 2

not the bit explozives the shoot up and pop in the air and the scraps come back down con u help

Answer 3

whats t then or do I have to find t

Answer 4

Yes, that's the only variable left. Without it, we would have numbers only and nothing to solve for :D

Answer 5

so the equation would look like 165=-16²+vt+s

Answer 6

165=-16t+110t+0

Answer 7

how would I start would I start with the exponent or the 110

Answer 8

Hang on a minute please.

Answer 9

You have to set it up as a quadratic equation...however, I need to check to make sure we have the correct values for all the variables.

Answer 10

Okay...

Answer 11

ok

Answer 12

H(t) = final height = 0
v = speed of firecracker = 110
s = initial height = 165

So the correct setup is

0 = -16t^2 + 110t + 165

Answer 13

ok that make more sense bc it has it = 0

Answer 14

next I think I have to find a gcf and divide by that or divide by 16

Answer 15

It doesn't always have to be = 0. But I guess if it wasn't you would have to use additional equations.

Answer 16

When solving quadratic equations, if you have a negative for the leading term, you'll want to try to get rid of it. There are two ways to do it. You can either add each term to the other side of the equation, or you factor out a negative:

0 = -(16t^2 - 110t - 165)

Then divide both sides by -1:

0 = 16t^2 - 110t - 165

Answer 17

It is probably best to use the quadratic formula to find t in this case.

Answer 18

can u tell me what the 1st step is to solve it then im pretty sure I can solve it form there I just need help getting started