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Projectile motion problem with components

  1. Sep 18, 2009 #1
    1. The problem statement, all variables and given/known data

    a ball is thrown up onto a roof, landing 3.90 s later at height h = 18.0 m above the release level. The ball's path just before landing is angled at θ = 67.0° with the roof. (a) Find the horizontal distance d it travels. (Hint: One way is to reverse the motion, as if on videotape.) What are the (b) magnitude and (c) angle (relative to the horizontal) of the ball's initial velocit

    2. Relevant equations

    i thought it was just v0x=vcostheta
    v0y=vsintheta

    and kinematics

    3. The attempt at a solution

    i really have no idea how to start this one
     
  2. jcsd
  3. Sep 18, 2009 #2

    kuruman

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    Homework Helper
    Gold Member

    What do you mean by "kinematics"? What you have written down is just the horizontal and vertical components of the initial velocity. That's not enough. Start by writing down the complete kinematics equations in 2-dimensions. Then we will have a starting point and if you don't know how to use them, we will help you along.
     
  4. Sep 18, 2009 #3
    d= vit + 1/2 at^2

    vf= vi + at

    vf^2= vi^2 + 2ad

    d= (vi + vf)/2 * t

    but i still don't know what to do
    i'm sorry, but i've been doing physics all day and my thoughts just aren't together
    and it's due in like an hour and a half :/
     
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