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Homework Help: Projectile Motion (basic problem)

  1. Feb 4, 2010 #1
    1. The problem statement, all variables and given/known data

    A ball is thrown with an upward velocity of 5 m/s from the top of a 10-m high building. One second later, another ball is thrown vertically from the ground with a velocity of 10m/s. Determine the height from the ground where the two balls bass each other.

    2. Relevant equations

    1) v=vot + at
    2) s=so + vot + 0.5at2
    3) v2 = vo2 + 2a(s-so)

    3. The attempt at a solution

    I know that this is a basic physics problem. I have taken University Physics 1 before, and made an A, but I am stuck in this problem lol.

    I am assuming that we do something like y1=y2 and then just solve the equation, get time. And then plug the time in. Or we can do t1=t2

    But I am having problem making the equations.

    I did this:

    y1=vo1t1 + 0.5at12

    Vo1 = 5 m/s
    a = 9.8 m/s2

    y2=vo2t2 + 0.5at22

    t1 = t2 - 1

    vo2 = 10 m/s

    The problem is, my t1 is coming out to be -11/7 Lol :)

    Please help!!

    Last edited: Feb 4, 2010
  2. jcsd
  3. Feb 4, 2010 #2
    y1 doesn't equal y2. The ball is being thrown from the building so their displacements will be different.
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