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Projectile Motion Question #2 help?

  1. Feb 14, 2009 #1

    J89

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    1. The problem statement, all variables and given/known data
    In a carnival booth, you win a stuffed giraffe if you toss a quarter over a small dish. The dish is on a shelf above the point where the quarter leaves your hand and is a horizontal distance of 2.1 m from this point. If you toss the coin with a velocity of 6.4 m/s at an angle of 60 degrees above the horizontal, the coin lands in the dish. You can ignore air resistance.

    a) What is the height of the shelf above the point where the quarter leaves your hand?
    b) What is the vertical component of the velocity of the quarter just before it lands the dish?




    2. Relevant equations
    x=(V0cosa0)t
    y=(V0sina0)t - 1/2gt^2
    Vx=V0cosa0
    Vy=V0sina0-gt



    3. The attempt at a solution
    I figured part A and the answer is 1.5 m, but for Part B I got -0.93 m/s when I attempted, but the actual answer is -0.89 m/s. I used Vy=V0sina0-gt, where t is .66 s which you get from doing Part A. Help!!
     
  2. jcsd
  3. Feb 15, 2009 #2

    Delphi51

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    Homework Helper

    Rounding t to .66 is inadequate. If you wish to have 2 digit accuracy in the final answer you need at least 3 digits in calculations.

    Oh, I get -0.895 m/s which I would round to .90 so I disagree with the -.89, too!
     
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