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Homework Help: How high is the building?

  1. Sep 12, 2008 #1
    greetings :)

    so i'm pretty stumped on this one question from masteringphysics:

    A ball thrown horizontally at 23.7 m/s from the roof of a building lands 35.0 m from the base of the building. How high is the building?

    i first listed all of my given values
    v_x0 = 23.7 m/s
    a = a_y = -g = -9.8 m/s^2
    x = 35 m
    x_0 = y_0 = 0
    v_y0 = 0
    a_x = 0
    t = ?
    y = ?

    used the horizontal motion formula to find t

    x = x_0 + v_x0 t + 1/2a_x t^2
    t = 35/23.7 = 1.5s

    and then the vertical motion formula to find y with the time i found above

    y = y_0 + v_y0 t - 1/2gt^2
    y = -1/2 (9.8)(1.5^2)
    y = 11.025m


    they said that this answer is "not quite", but i went over my calculations and still got 11.025 m. did i plug in the wrong values or used the wrong formulas?

  2. jcsd
  3. Sep 12, 2008 #2
    i just realized i've posted this onto the wrong thread. my apologies
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