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Homework Help: Velocity/Speed Problems (Studying for exam)

  1. Aug 28, 2011 #1
    1. The problem statement, all variables and given/known data
    A person throws a ball with 13,5 m/s straight up. Calculate the maximum height that it will reach from the point where it was thrown. Also find the velocity when the ball is 1.50m above the starting point.

    Sorry if the problem is hard to understand, had to translate it from spanish, hopefully it's clear enough.

    2. Relevant equations
    Vx = V0x + axt
    x = x0 + v0xt + 1/2 ax t^2

    3. The attempt at a solution
    13.5m/s = 0 + 9.81 * t
    13.5/9.81 = t
    t = 1.38 s (what it took to reach the highest point)

    x = 0 + 13.5 * 1.38 + 1/2 * -9.81 * 1.37^2
    x = 9.42 m (maximum height?)

    Not sure if the problem is correct, if it's not any guidance is appreciated. I'm also missing what's the velocity 1.50m above the starting point.
     
  2. jcsd
  3. Aug 28, 2011 #2

    lewando

    User Avatar
    Homework Helper
    Gold Member

    t is correct (1.376 s), but you are using 1.38 and 1.37^2 in the same equation. Hang on to the couple extra digits until you have the final result.

    You know x0, x, Vx0, and a. There is a kinematic equation that you have not posted that will allow you to find vx directly.
     
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