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Homework Help: Movement in x,y line

  1. Sep 6, 2012 #1
    1. The problem statement, all variables and given/known data
    From a height 40 meters up, one throw a ball with the velocity of 20 m/s. The elevation is 0°. How far does the ball come?

    vo = 20 m/s
    x = 40 meters
    α = 0°

    2. Relevant equations

    y = v0 × t × sinα - (9.82×t2)/2

    x= v0×t×cosα

    3. The attempt at a solution
    I put what I know in there

    40 = 20×t×sin0° - (9.82×t2)/2
    80/9.82 = t2
    √(80/9.82) = t = 2.85 s (Is that right?)

    Then I put all I know in the other formula to get x:
    x= v0×t×cosα

    x = 20×2.85×cos0°
    x=57 meters
    (Doesn't that feel a little too short?)

    I've no answer to this question and I would be really glad if someone could confirm that this is correct calculated :)
    Edit: There's no air resistance
  2. jcsd
  3. Sep 6, 2012 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Looks good to me.
  4. Sep 6, 2012 #3
    I hope so. Thanks for checkin' it :)
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