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anonymous

  • one year ago

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

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  1. anonymous
    • one year ago
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    @gina123 @gina123

  2. anonymous
    • one year ago
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    @Michele_Laino @ganeshie8

  3. anonymous
    • one year ago
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    i think the answer is 7 seconds

  4. anonymous
    • one year ago
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    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

  5. anonymous
    • one year ago
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    ok i understand that but im unsure of how to solve it

  6. anonymous
    • one year ago
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    Do you know the quadratic formula?

  7. anonymous
    • one year ago
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    yes, so i would just use that?!!!

  8. anonymous
    • one year ago
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    Yes. DO you see how the formula resembles a quadratic. The only difference is that it is a t and not an x

  9. anonymous
    • one year ago
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    You should get 6.53. That rounds to 7.

  10. anonymous
    • one year ago
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    -16 t^2 + 100 t + 140 = 0 I forgot the negative.

  11. anonymous
    • one year ago
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    ok yes i got that answer thanks so much!!!!!!! ;)

  12. anonymous
    • one year ago
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    No problem!!

  13. anonymous
    • one year ago
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    do you mind helping with one more?

  14. anonymous
    • one year ago
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    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?

  15. anonymous
    • one year ago
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    Sure

  16. anonymous
    • one year ago
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    height + velocity + gravity https://www.youtube.com/watch?v=K7b-da1o3BY

  17. anonymous
    • one year ago
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    Well what do you know? What is your initial velocity and initial height?

  18. anonymous
    • one year ago
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    the velocity is 34 feet and i believe the unital height is 0 feet

  19. anonymous
    • one year ago
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    assuming since the problem doesnt say

  20. anonymous
    • one year ago
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    for the height

  21. anonymous
    • one year ago
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    Yup. So plug them into the equation for v and s

  22. anonymous
    • one year ago
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    H(t) = -16t2 + 34t + 0

  23. anonymous
    • one year ago
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    yes so the answer would be 18.1 feet ??

  24. anonymous
    • one year ago
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    Yeah!

  25. anonymous
    • one year ago
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    Thanks so much for walking me through it!!!!!!!

  26. anonymous
    • one year ago
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    You're welcome (:

  27. anonymous
    • one year ago
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    Medal?

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