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Projectile's final velocity

  1. Oct 13, 2016 #1
    1. The problem statement, all variables and given/known data
    A rock is thrown from a cliff that is 50m long with an initial velocity of 7m/s and an angle of 53, find the rock's veloctity before it hits the ground

    2. Relevant equations
    vfy=sin(theta)*vi-gt
    vf^2=(vi*sin(theta))^2-2gy

    3. The attempt at a solution
    x=vi*cos()t
    t=x/(vi*cos)
    x=7*cos(53)-2*9.81*(x/(vi*cos(53)))^2
    x =2.49 or x=-6.11
    at this point i tried to plug in x into vf^2=(vicos)^2-2gy
    but none of them give 32 m/s which is the answer according to the answer's sheet
     
  2. jcsd
  3. Oct 13, 2016 #2
    Some questions for you to consider:
    In your solution what is x? It appears you are using x to represent two different quantities.
    Why do you think the time of flight is given by your second equation?
     
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