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Homework Help: Motions on 2 dimensions

  1. Sep 30, 2008 #1
    1. The problem statement, all variables and given/known data
    A playground is on the flat roof of a city school, 6.00m above the street below. The vertical wall of the building is 7.00 m high forming a 1m high railing around the playground. A ball has fallen to the street below and a passerby returns it by launching it at an angle of 53 degrees above the horizontal at a point 24 m from the base of the bulding wall. The ball takes 2.20 to reach a point vertically above the wall.

    Find the vertical distance by which the ball clears the wall.

    2. Relevant equations

    3. The attempt at a solution

    I can get the initial velocity first by plugging in the formula:

    24 = Vi*cos(53)*(2.2) then

    finding for Vi I get 18.1. Now how do I find the height the ball clears the wall?
    Last edited: Sep 30, 2008
  2. jcsd
  3. Oct 1, 2008 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    You need an equation that has the distance the acceleration and the initial and final velocities in the y direction. You know at the max height the velocity in the y direction will be zero. You know the initial velocity and the acceleration and thus you can work out the height.
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