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physics

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Marie shoots an arrow vertically upward at a sandhill crane. If the arrow travels to a maximum height of 99.5 meters, calculate how fast it was shot.
And, for how much time was Marie's arrow in the air?

  • physics - ,

    v = Vi - 9.8 t
    0 = Vi - 9.8 t
    Vi = 9.8 t

    99.5 = Vi t -4.9 t^2
    99.5 = 9.8 t^2 - 4.9 t^2 = 4.9 t^2
    t = 4.5 seconds to top
    so
    Vi = 9.8 * 4.5 = 44.2 m/s

    You could also do this by conservation of energy
    (1/2) m Vi^2 = m g h
    so
    Vi = sqrt (2*9.8*99.5)
    = 44.2 m/s

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