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Physics and algabra

  1. Apr 15, 2004 #1
    What is the answer to how fast a ball fall's form 25 feet useing the formula d = 16t2 :confused:
     
  2. jcsd
  3. Apr 15, 2004 #2
    [tex]d = 16t^2[/tex]

    I assume that this gives the distance in feet. So,

    [tex]t = \sqrt{25/16}[/tex]

    However you want the velocity of the ball at t = that number above. Can you finish now?
     
  4. Apr 15, 2004 #3
    physics and algebra

    I think the answer is 1 1/4 or 5/4 can you tell me if i am on the right track.? :rolleyes:
     
  5. Apr 16, 2004 #4

    HallsofIvy

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    Staff Emeritus
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    Yes, that is correct.
     
  6. Apr 16, 2004 #5
    This is only the time, not the velocity at that time. You still need to find velocity as a function of time. Can you do that?
     
  7. Apr 17, 2004 #6
    if you find the first derivative of distance as a function of time this wud give you a formula for velocity if acceleration is not constant, in this case it wud be
    d'(t) = 36t.
     
  8. Apr 17, 2004 #7

    Judging by the title, I don't think Joseph would know calculus. However, I could be wrong.
     
  9. Apr 17, 2004 #8
    Eh. . . The acceleration is constant. your post should read: "If you find the first derivative of distance as a function of time this would give you a formula for velocity, in this case it would be d'(t) = 36t."
     
  10. Apr 17, 2004 #9
    Froget calculus; judging by this, "d'(t) = 36t" and the number of times it's been quoted in the last few posts, I don't think anyone here knows what 2*16 is!
     
  11. Apr 18, 2004 #10

    rj

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    hey,
    d = u*t + 1/2 a*t2
    => 25 = 1/2 g*t2 ....................(1)
    but according to the question
    d = 16 t2
    or
    25 = 16t2.................................(2)

    comparing (1) and (2)
    1/2g=16

    g= 32 feet/ second squared ??

    or 12.8 metres/second squared ??

    was the ball really undergoing a free fall ??
     
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