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A rock is thrown directly upward from the edge of the roof of a building that is 40.2 meters tall. The rock misses the building on its way down, and is observed to strike the ground 4.00 seconds after being thrown. Neglect any effects of air resistance. With what speed was the rock thrown?

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  1. h = 40.2 + Vi t - 4.9 t^2
    at ground h = 0
    4.9 t^2 - Vi t - 40.2 = 0
    = 4
    so solve for Vi

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