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Homework Help: Finding Velocity via Convervation of Energy

  1. Mar 2, 2009 #1
    1. The problem statement, all variables and given/known data
    A projectile is shot upward from the top of a cliff in an angle of 25 with a velocity of 195 m/s.The height of the cliff is 315m. What will be its speed when it strikes the ground below? (Use conservation of energy)



    2. Relevant equations
    Ok...initial energy = final energy

    Initial energy = .5m*(initial velocity square) + mgy
    Final energy = .5m*(final velocity square)

    initial velocity = sin*theta*upward initial velocity = sin25*195


    3. The attempt at a solution

    So I set them to equal and I got final V to be 114, but it says I had it wrong, canceling out the mass.... I have no clue what I did wrong there...
     
  2. jcsd
  3. Mar 2, 2009 #2

    Delphi51

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    Homework Helper

    should not be used in this one. It is an energy problem, not a 2D motion analysis. Just use the 195 in the first 1/2m*v^2.
     
  4. Mar 2, 2009 #3
    OK, thank you! =)
     
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