## anonymous one year ago I need somebody to walk me through this, I understand the just of it. PLease Help! Medal and Fan!

1. anonymous

@dan815

2. anonymous

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3. anonymous

@AllAmericanViking

4. anonymous

@Donblue

5. anonymous

@ganeshie8

6. anonymous

@nincompoop

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8. anonymous

The function H(t) = -16t2 + vt + s shows the height H(t), in feet, of a projectile launched vertically from s feet above the ground after t seconds. The initial speed of the projectile is v feet per second. Part A: The projectile was launched from a height of 96 feet with an initial velocity of 80 feet per second. Create an equation to find the time taken by the projectile to fall on the ground. (2 points) Part B: What is the maximum height that the projectile will reach? Show your work. (2 points) Part C: Another object moves in the air along the path of g(t) = 31 + 32.2t where g(t) is the height, in feet, of the object from the ground at time t seconds. Use a table to find the approximate solution to the equation H(t) = g(t), and explain what the solution represents in the context of the problem? [Use the function H(t) obtained in Part A, and estimate using integer values] (4 points) Part D: Do H(t) and g(t) intersect when the projectile is going up or down, and how do you know? (2 points)

9. anonymous

Is this FLVS?

10. anonymous

Yep!

11. anonymous

Algebra?

12. anonymous

Algebra 1 semester 2, just this and im done the whole thing

13. anonymous

did you plug in the numbers to create the equation for A?

14. anonymous

i tried to but didnt quite understand

15. anonymous

Ok I just finished it yesterday. Maybe I can see if I had it too

16. anonymous

this is what i got H(t) = -16(96)^2 + 80(96) + 96

17. anonymous

$$H(t)=-16t^2+vt+s$$ is the basic equation. You need to replace the v with the velocity they gave you, and replace the s with the initial height. t is the variable, so it stays the same.

18. anonymous

all you need to do is change v to 80 and s to 96

19. anonymous

so the velocity is 80 fps and the height is 96 but whats the time?

20. anonymous

?

21. anonymous

22. anonymous

time is the independent variable. the projectile has a different height for different values of time. It's 96 in the beginning and then goes up and comes back down

23. anonymous

i actually do need time to type, you know?

24. anonymous

sorry, okay s it would be H(t) = -16t^2 + 80t + 96?

25. anonymous

yes

26. anonymous

Sweet! now could you help with b?

27. anonymous

would you solve for t?

28. anonymous

Yes, for B, the height's going to be the y-coordinate of the vertex using the equation from a.

29. anonymous

$t=-\frac{ b }{ 2a }$ Look familiar?

30. anonymous

then once you have that t, plug it in to get the height

31. anonymous

Yes, okay soi got 5/2?

32. anonymous

that's the right time. now put it in for t in the equation from A

33. anonymous

$-16(5/2)^2+80(5/2)+96$

34. anonymous

oh okay, and then solve?

35. anonymous

yes

36. anonymous

i got 196?

37. anonymous

yes that's right

38. anonymous

C?

39. anonymous

for c, create a table for the values 0 through 5 and plug them into both equations

40. anonymous

You're looking for the t where you get the same (or pretty close) H for both equations

41. anonymous

okay let me see

42. anonymous

is it possible to solve algebraicly without a table?

43. anonymous

yes, but you probably haven't done it in algebra I. |dw:1436390010929:dw|

44. anonymous

you'd set the equations equal to each other then solve for t -16t^2 + 80t + 96 = 31+32.2t

45. anonymous

it's a standard quadratic equation, so maybe you've done that

46. anonymous

my bad didnt mean to type that

47. anonymous

both aanswers are rounded but i got t = -1, t = 4

48. anonymous

you want to go with 4 because time has to be positive

49. anonymous

okay, so thats the answer for c?

50. anonymous

yes

51. anonymous

for D, 4 seconds is after the max height at 2.5 seconds, so it's got to be on the way down

52. anonymous

okay, thank you so much! that really helped a lot :)

53. anonymous

you're welcome