Physics

A ball is thrown vertically and reaches a height of 25m. What was it's initial velocity?

asked by Haley
  1. v = Vi - g t
    at top v = 0
    so
    0 = Vi - 9.81 t
    Vi = 9.81 t

    h = Hi + Vi t - 4.9 t^2
    but t = Vi/9.81
    so
    25 = Vi (Vi/9.81) - 4.9 (Vi^2/9.81^2)
    25 = Vi^2 (.102 - .051)
    Vi^2 = 490
    Vi = 22.1
    alternatively
    (1/2) m Vi^2 = m g h
    or
    Vi = sqrt (2 g h)
    = 22.14

    posted by Damon

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