Projectile: Find initial velocity without time

  1. JJBladester

    JJBladester 286
    Gold Member

    1. The problem statement, all variables and given/known data
    Knowing that snow is discharged at an angle of 40 degrees, determine the initial speed, v0 of the snow at A. Answer: 6.98 m/s

    2. Relevant equations



    3. The attempt at a solution

    I have found the x and y velocity and position formulas. Now since I don't know time, should I solve both position equations for time (t) and set them equal to each other to get my only unknown, vi? The quadratic equation for time in the y-dir seems a bit hectic. Is there an easier way to go about trying to find vi?
    Last edited: Sep 11, 2010
  2. jcsd
  3. kuruman

    kuruman 3,449
    Homework Helper
    Gold Member

    Start with
    L = v0 t cosθ
    Δy = v0 t sinθ - (1/2) g t2

    Solve the first equation for t and replace in second equation. Solve the ensuing equation for v0.
  4. JJBladester

    JJBladester 286
    Gold Member

    I believe this is what you had in mind. The answer matches the professor's answer. Thanks again kuruman!

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