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Max. q

  1. Jan 15, 2007 #1
    my teacher gave me this q:
    a snowball if thrown into the air. The function h= -4.9t^2 + 20t + 1.8 expresses the relationship between height, h, in meters and time, t, in seconds.
    a) algebraically determine the max height the snowball reaches
    b) how long is the snowball in the air?

    i know to solve b you just need to plug in your h and solve for t. however for part a, i am not sure how to solve the max. can someone help?
  2. jcsd
  3. Jan 15, 2007 #2
    Do you have an equation for the velocity of the projectile as a function of time?

    If not, do you know that velocity is the derivative of position with respect to time?

    In either case, note that the ball reaches its maximum height when the velocity is zero.
  4. Jan 15, 2007 #3
    no, all the info i got to solve this q i posted
  5. Jan 15, 2007 #4


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    Have you studied calculus?
  6. Jan 15, 2007 #5


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    h= -4.9t2+ 20t+ 1.8 is a quadratic. Its graph is a parabola with vertex at the top. Complete the square to find the vertex. You don't need to use calculus.
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