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Projectile question

  1. Oct 14, 2009 #1
    1. The problem statement, all variables and given/known data
    A ball is tossed from an upper-story window of a building. The ball is given an initial velocity of 9.00 m/s at an angle of 16.0° below the horizontal. It strikes the ground 5.00 s later. (Ignore air resistance.)
    (b) Find the height from which the ball was thrown.

    2. Relevant equations

    Y-Yo= Vyot -1/2gt^2

    3. The attempt at a solution

    Yo= -Vyot +1/2gt^2

    Yo= -(9sin16)(5) + 1/2(9.8)(25) = 110m
    but the answer is wrong.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 14, 2009 #2


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    Homework Helper

    Consider the sign of vyo.

  4. Oct 14, 2009 #3


    Staff: Mentor

    Your formula above is incorrect. The ball is tossed out of the window at a downward angle. This means that the vertical component of the velocity is in the same direction as gravity is acting. In your formula, Vy0 is negative, but the gravitational force is positive. You can define which sign corresponds to up or down, but you have to be consistent.
  5. Oct 14, 2009 #4
    Thank you!
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