physics please help

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A hoodlum throws a rock straight down from the roof of a building 109m high. If it takes 2.40s to hit the ground below, with what initial speed was the rock thrown?

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  • physics please help -

    If thrown down with initial velocity v, then just solve

    109 - vt - 4.9t^2 = 0

    plug in t=2.40 and find v.

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