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Finding the Velocity

  1. May 2, 2012 #1
    1. The problem statement, all variables and given/known data
    screenshot of problem: imgday.net/?di=8RMN


    2. Relevant equations
    PE = MGH
    KE = 1/2 x m x v^2
    V = d/t


    3. The attempt at a solution
    I know how to find the PE & KE, but I stumped at finding the velocity and it keeps saying I get the wrong answer or would it just be 20 m/s?
     
  2. jcsd
  3. May 2, 2012 #2

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    The above formulas are very important to solving this problem.
    Be careful with that one. v = d/t only applies for constant velocity (i.e. if a = 0). But acceleration is involved with this problem. The projectile is certainly not moving at a constant velocity.
    The answer may just be 20 m/s, but you should be able to explain why that is.

    If you've already found KE, then use your KE = ½mv2 formula. Solve for v. :wink:
     
  4. May 2, 2012 #3
    Oh, thank you so much for the tidbit. My physics teacher never explained to us like that. It's true that you learn something new everyday. :)

    It's not 20 m/s, it's 20.976 and rounded to 20.98, isn't it because speed & velocity are teh same thing?

    I wish I thought of that earlier, now I got the correct answer using that formula! I feel so dumb for wasting so much time trying to figure it out.
     
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