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Homework Help: Projectile Vertical Velocity

  1. Sep 23, 2010 #1
    1. The problem statement, all variables and given/known data

    A Soccer ball is projected at a certain angle (ϴ) above the horizon. It travels a horizontal distance of 1.2x102m in 3.0s.

    a) Find the horizontal velocity
    b) Find the initial vertical velocity (VV1).
    c) Find the magnitude and direction of the initial velocity (VI)


    2. Relevant equations

    V = d/t

    VH = VIcosϴ
    VV1 = VIsinϴ

    (Subscript H denotes the horizontal axis and Subscript V denotes the vertical axis)


    3. The attempt at a solution

    I know how to do Part a):

    dH = v/t
    dH = 120 / 30
    dH = 40 m/s [Forward]

    Part b confuses me. It seems to me like there is some information missing that causes me to not be able to do it but the teacher has told me that all the information that I need is there. I'll be able to get part C if somebody can help me out with b).

    This is Grade 12 Physics and I haven't taken Calculus yet.


    Thanks to anybody who can help me out.


    The answers on the sheet are:
    a) 40 m/s
    b) 15 m/s
    c) 43 m/s [20o to the horizon]
    1. The problem statement, all variables and given/known data


    Thanks in advance for any help that you can give me!
     
  2. jcsd
  3. Sep 23, 2010 #2
    Well, right after I posted it, the answer hit me so never mind.

    V2 = V1 + at
    0m/s = V1 + (-9.81m/s2)(1.5s)
    V1 = 14.7 m/s [up]


    Thanks anyways!
     
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