anonymous
  • anonymous
Math help please! 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? (4 points) Five seconds Seven seconds Nine seconds 11 seconds
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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chestercat
  • chestercat
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anonymous
  • anonymous
@gina123 @gina123
anonymous
  • anonymous
@Michele_Laino @ganeshie8
anonymous
  • anonymous
i think the answer is 7 seconds

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More answers

anonymous
  • anonymous
Okay so here you have your equation H(t) = -16t2 + vt + s You are given the initial height = 140 = s And the initial speed = v = 100 ft/s 16 t^2 + 100 t + 140 = H(t) Since you want to find the time it took to hit the ground, you are looking for the x intercept. Set the equation equal to 0 then use the quadratic formula. 16 t^2 + 100 t + 140 = 0
anonymous
  • anonymous
ok i understand that but im unsure of how to solve it
anonymous
  • anonymous
Do you know the quadratic formula?
anonymous
  • anonymous
yes, so i would just use that?!!!
anonymous
  • anonymous
Yes. DO you see how the formula resembles a quadratic. The only difference is that it is a t and not an x
anonymous
  • anonymous
You should get 6.53. That rounds to 7.
anonymous
  • anonymous
-16 t^2 + 100 t + 140 = 0 I forgot the negative.
anonymous
  • anonymous
ok yes i got that answer thanks so much!!!!!!! ;)
anonymous
  • anonymous
No problem!!
anonymous
  • anonymous
do you mind helping with one more?
anonymous
  • anonymous
Darlene kicks a soccer ball off the ground and in the air, with an initial velocity of 34 feet per second. Using the formula H(t) = -16t2 + vt + s, what is the maximum height the soccer ball reaches? (4 points) 17.7 feet 18.1 feet 19.3 feet 20.2 feet Im getting 17.7 feet?
anonymous
  • anonymous
Sure
anonymous
  • anonymous
height + velocity + gravity https://www.youtube.com/watch?v=K7b-da1o3BY
anonymous
  • anonymous
Well what do you know? What is your initial velocity and initial height?
anonymous
  • anonymous
the velocity is 34 feet and i believe the unital height is 0 feet
anonymous
  • anonymous
assuming since the problem doesnt say
anonymous
  • anonymous
for the height
anonymous
  • anonymous
Yup. So plug them into the equation for v and s
anonymous
  • anonymous
H(t) = -16t2 + 34t + 0
anonymous
  • anonymous
yes so the answer would be 18.1 feet ??
anonymous
  • anonymous
Yeah!
anonymous
  • anonymous
Thanks so much for walking me through it!!!!!!!
anonymous
  • anonymous
You're welcome (:
anonymous
  • anonymous
Medal?

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