PLEASE HELP ME!!! =)
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?

Question

PLEASE HELP ME!!! =)
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?

anonymous · Answer

Would the equation be h(t) =-16t^2 +140t +100 ?

sissyedgar · Answer

Im not really sure, but i tink ur rite on ur formula!

anonymous · Answer

Okay thanks =)

sissyedgar · Answer

ur welcome

anonymous · Answer

@e.mccormick @Nnesha @pooja195

jim_thompson5910 · Answer

v = initial speed
v = 100

s = initial height
s = 140

anonymous · Answer

And it takes it nine seconds to hit the ground, correct?

jim_thompson5910 · Answer

Incorrect. You have v and s mixed up.

anonymous · Answer

Oh, i'm sorry, so could you explain pls ?

jim_thompson5910 · Answer

do you see how v = 100 and s = 140?

jim_thompson5910 · Answer

v = initial speed or velocity
s = initial height

anonymous · Answer

Yes sir =)

jim_thompson5910 · Answer

so your equation should be $$\Large h(t) = -16t^2 + 100t + 140$$

jim_thompson5910 · Answer

it hits the ground when h(t) = 0 which is why you need to solve $$\Large 0 = -16t^2 + 100t + 140$$

anonymous · Answer

okay thx =)

anonymous · Answer

so it's seven seconds?

jim_thompson5910 · Answer

did you round to get 7? or did you get exactly 7?

anonymous · Answer

I rounded

anonymous · Answer

Is that wrong?

jim_thompson5910 · Answer

what did you get before you rounded?

anonymous · Answer

7.428

jim_thompson5910 · Answer

I'm getting 7.427978620 which is basically what you have. Nice work.

anonymous · Answer

lol Thanks =)

jim_thompson5910 · Answer

you're welcome